Talk:History of IBM magnetic disk drives

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Winchester Blvd[edit]

It was my (admittedly undocumented) impression that the Winchester Disk was named not for the Winchester Rifle, but for the location of the IBM office on Winchester Blvd in San Jose. Perhaps this is an urban legend but I recall hearing it many years ago. Jim Bowery 23:35, 19 September 2006 (UTC)

Added IBM source to article. 30-30 must be a Winchester [rifle] tooold (talk) 06:35, 21 January 2009 (UTC)
The folklore I've heard is that the technology was named Winchester after the rifle, because the team was working on dual 30 MB drives (30+30 MB), hence the "30-30" connection with the rifle. — Loadmaster (talk) 01:09, 22 March 2013 (UTC)
Ken Haughton code named it Winchester for the rifle because the program was initially two thirty MB spindles in a box, called "30 - 30" by some. See his oral history, p.9. Tom94022 (talk) 05:32, 22 March 2013 (UTC)

The folklore about Winchester road name was widespread in the years I worked at the San Jose plant. This may be a case where a name was suggested and multiple reasons were found to sustain it.HiTechHiTouch (talk) 01:27, 3 March 2016 (UTC)

Note that these two lines of folklore are connected. Winchester Blvd was named for Winchester House, which was built by Sarah Winchester, who inherited 50% of the Winchester Repeating Arms Company, inventor of the .30-30 Winchester center fire cartridge. 02:58, 3 March 2016 (UTC)

The source of the urban legend about the boulevard is not known, but it is clear from Haughton that the name came from the rifle. Given the bredth of the urban legend it might be worth an in-line note in the article debunking it. Tom94022 (talk) 18:37, 3 March 2016 (UTC)


Drive sizes are listed as "decimal digits" and "characters". What are they in bytes or bits or octets? - Omegatron 15:41, May 13, 2005 (UTC)

And make sure to remember the difference between megabytes and mebibytes.

decimal digits were either 4 or 5 bits plus 1 parity bit; characters were either 6 (BCDIC) or 8 (EBCDIC) bits plus 1 parity bit. -- 00:23, 18 March 2006 (UTC)

Number of platters[edit]

I used to work with these things and I'm fairly sure they had six platters not five. However the top surface of the top platter and the bottom surface of the bottom platter were not used so there were ten surfaces coated with the magnetic material, giving ten tracks per cylinder. The reason the outside surfaces were not used is that they were liable to be touched when the disk was removed from its drive. In fact operators would place their hands on the top surface to slow them down. This led at least one manufacturer to coat the top with abrasive.

Here is a photograph of the disk which shows six platters. If anything this one is even clearer. Is this enough proof to merit editing the article? --R Cornwell 13:20, 4 May 2006 (UTC)

I fixed it under 2311. The section on the 1311 had it right. --agr 19:11, 4 May 2006 (UTC)


IBM 3380 redirects here, but this article doesn't say anything about it. A netnews article I read suggests that there are still some in operation. 121a0012 19:06, 5 May 2006 (UTC)

Thanks, I've added some info.--agr 00:07, 11 May 2006 (UTC)

Tub file?[edit]

I'm not sure what is meant by "the punch card tub file used by most businesses of the time." Please elaborate.--agr 03:24, 20 September 2006 (UTC)

2311 rememberances[edit]

The shop where I got my first operators job had a string of 4 2311s and here is what I remember about them.

One of the previous posts mentioned operators slowing them down with their hands. There were really 2 parts to a 2311, and all the disks until Winchester. There was the drive that contained the electronics, drive motors, and heads. There was also the disk pack. Storage was so expensive, thousands of dollars for one 7MB drive, that nobody thought of having all their data online and it was not necessary since everything was batch jobs. So, you would have a pack for your payroll files, one for the GL, etc. When you ran a job you would have to mount the packs that contained the data.

Push the stop button and the drive would spin down but this took forever and who has the time? When you opened the lid there was something that engaged to prevent the disk from turning. If you just opened the top on a spinning disk this would take some damage so that was out. If you just opened the top a little you could reach up under it and get your fingers on the top platter and slow it down. I don't think lawyers to sue had been invented yet.

Once it sopped you opened the top and took the top of the case, a clear plastic tub with a handle on the top, put it over the disk. Spinning the top would attach it to the top of the disk and detach the disk from the drive. You lifted it up and stuck the bottom on to keep some of the crud out.

I don't see how any PC person can conceive of the size of one of these things. The pack was about 16 inches in diameter by about 6 inches high. In this massive area the drive could write 100 or 200 tracks (I think the 2311 had 100 and the 2314 had 200. the 2314 also doubled the number of platters) In fact when you were doing a backup of the drive you could tell how far you had gotten by going over to the drive and looking down through the glass top. The arm holding the heads came straight out from the side and on to of it was a scale with the tracks marked. You could literally look down and see what track you were up to.

Now, everybody knows that the heads are moved by that nice clean voice coil. Not the 2311s. They were hydraulic. Nice little pump, hoses, pistons, etc. In fact one of our 2311s had a small leak and when the CE came in to do preventative maintenance (There was so much mechanical stuff associated with a computer that every week the guy form IBM came and spend a few hours trying to fix things before they broke.) he would get a hand full of the little bits from the card punch and literally put them inside the disk drive to soak up the oil. —The preceding unsigned comment was added by P7willm (talkcontribs) 15:49, 22 March 2007 (UTC).

Jan 14 2014 I worked on the 2311, 3330, and 3380 disk drives as an IBM CE. The hydraulics in the 2311 were always leaking. I used to calim the drive would not work if there was no hydraulic oil in the base. When you removed the cover of the hydraulic unit there was another cover inside that covered the hydraulic pistons. To replace one of the pistons or make adjustments you had to remove that cover. If you forgot to put it back on, and you manually actuated the hydraulic unit it would squirt oil several feet into the air, then you had a real mess to clean up.

William H. — Preceding unsigned comment added by (talk) 00:56, 15 January 2014 (UTC)

Great memories! That time is completely different from what's currently perceived by an average "PC era" user... While nowadays you can buy a quite reliable 1 TB HDD for peanuts (when compared to those old storage prices), I don't think people became much smarter and more productive, especially not as many times as storage technology advanced. — Dsimic (talk) 00:04, 16 January 2014 (UTC)

The floppy disk[edit]

This text "Another important IBM innovation was little noticed when it was introduced initially with the System 360, in the 2835 Storage Control for the 2305 Drums, to be attached to the high end processor models 2075 and 2095. Then it became more popular with introduction of the System/370 in 1971. IBM needed a way to load new microcode into the IBM Storage Control Units 2835 and 3830, and into the IBM System/370 Model 155 and developed the 23FD floppy disk 'read only' for this purpose."

needs help. The first two "it"s are unknown references, other than "important IBM innovation". The text begins with the 2835, advances the time with "Then it became" to describe the System/370, then writes about both "2835... and 370 model 155" as if the two were at the same time.

Suggest saying first what the innovation is, followed by implementations sequenced by time.tooold (talk) 05:33, 21 January 2009 (UTC)

The subject is well covered in other articles, so I shortened the section to the bare minimum and linked to the most appropriate article/section. Tom94022 (talk) 06:17, 21 January 2009 (UTC)


The article is about Early disk storage. "Early" is a relative term. Regardless of what it means, it should be used consistently. The article mentions that IBM sold its disk operations to Hitachi in 2002. It discusses 3.5 inch HDDs as of 2004. However, it leaves out RAMAC Virtual arrays. The RAMAC introduced in 1989, unrelated to the original RAMAC, used 3.5 inch RAID 5 arrays, 5 drives per drawer. One of the drawers was a dynamic spare. Each unit held up to 90GB when all other drawers were populated. It had a built in controller that connected to up to 4 fiber optic channels. It had three levels of cache: drive level, drawer level, and unit level. It used algorithms to pre-cache based on areas of disk likely to be read.

It emulated 3380 or 3390 drives (and 3880/3990 controllers), and although systems programmers continued to allocate space at the "physical" level, it was truly virtual. In case of a drive failure, it would "phone home" to IBM, and start migrating to the spare drawer, optimizing performance for ongoing operations. IBM maintenance staff could hot swap drives, literally creating situations where computer room staff was unaware that anything had failed, and no noticeable degradation in performance had occurred. These were somewhere in the million dollar range, but the savings in floor space, energy and monthly maintenance made them competitive with older existing 3380 and 3390 drives.

Anybody who had to restore a mainframe after a failed 3380 can appreciate the importance of this alone, not to mention the performance gain. However, I mention all of this because even if you don't consider this "early," it predates the 2002 period mentioned as the end of the era. It also serves as a basis to compare 33xx technology to 3.5 inch drives, since these were the ones that were direct replacements for "early" technology, not the 2004 3.5 inch drives mentioned in the article.

It makes no sense to end things at 2002, and consider 2004 a fair point for comparison. If 2002 3.5 inch drives were to be used for comparison, the fastest of which were used in the latest generation of RAMAC, they not only could be used as a starting point for the "raw" comparison, but could more accurately reflect the true performance edge that they gave to mainframes compared to the "early" drives that they replaced.

--Hagrinas (talk) 17:48, 18 May 2009 (UTC)

I agree that the ending is inappropriate, my choice would be to end with the 3390 which is the end of IBM's mainframe line of disk drives, sometimes called SLEDs (Single Large Expensive Disks). After the 3390 the IBM world went to arrays of which RAMAC is just one of many so I would not add in the RAMAC Array or for that matter any other subsystem product to this article. Probably the article should be renamed IBM Mainframe Disk Drives (the 3370 would then be dropped). A separate article on storage subsystems would be the appropriate place for the RAMAC and its ilk. Any other thoughts Tom94022 (talk) 23:13, 18 May 2009 (UTC)
I think the scope should be the history of IBM disk drives up to the beginning of the PC/RAID era. I have no problem adding 3390 (the physical/virtual stuff is very interesting) and I would end with a mention of the new RAMAC and IBM and the market's switch to RAID technology, referencing the RAID article as the main article. I would still include a comparison to consumer grade disks because the extent of progress, while keeping the same basic architecture introduced in the the 1405, is so dramatic, perhaps unequalled in human history. However, I would not limit the article to mainframe disks. IBM did not make that distinction through the 1960's. Indeed, the RAMAC 305 was a midsized machine, as were the 650 and 1401. IBM 1311's were sold with the 1620, a low end machine; while the earliest use of the floppy was to load microcode on 360s that were mainframes. Early IBM mainframe installations (700 - 7000 series) generally did not include disk drives; they were too small (in capacity) and too slow to be of much use in most commercial mainframe shops, and their potential was not recognized in scientific shops (IBM operating systems did not include file management). Tape ruled. There are so few IBM pre-PC drives that were exclusively for small machines, e.g. the 2315, that I see no need to exclude them. --agr (talk) 11:33, 28 May 2009 (UTC)
  • I don't want to get into a semantics debate, but all those early computers are mainframes, small, large, scientific, commercial, etc - at least that's what the US government alleged in the anti trust suit. IMO the computer industry and the disk drive industry first changed with the emergence of the mini-computers. Since most of the disk drives in the article were only offered on IBM mainframes and IBM was very successful in these mainframe SLEDs, I'd rather limit the scope to what's there, enhance it and focus on IBMs successes with its SLEDs rather than bring in all the extraneous stuff about low end drives, where IBM was less than successful. I suppose I could retitle the article IBM SLED History (Single Large Expensive Disk Drives) :-)
  • I believe you are very mistaken about the low end of IBMs disk drive family both as to number of products and their relative production quantity (the first disk drive product line to exceed 100,000 units was the CDC SMD circa 1981 and that took 7 years, today a volume product does that in three days). Off the top of my head, the low end IBM disk drive line included the 2315, 5444, 3370, 62GV, G2PC, 681, Sawmill and others. The 2315 and 5444 class drives were used by all mini's in the early 70s, but most were made by other than IBM. And I bet the IBM 1130 outsold most if not all S/360's.
  • The PC era starts in 1983 while the RAID era for IBM mainframes starts in either 1991 with EMC or 1994 with the RAMAC, so I am unclear as to when you would end it. BTW, the first IBM RAID was the IBM 9337 in 1992 for the AS/400 a mini, not a mainframe.
So without agreement on scope, I guess the article stays as is :-( Tom94022 (talk) 20:01, 28 May 2009 (UTC)


Please tell me in plain English for non-native people, what means the following saying in the introduction: a stellar improvement. Does it mean 'great improvement' or 'fast improvement'? --Sibazyun (talk) 07:35, 13 September 2009 (UTC)

It's gone, see if what i wrote makes more sense. Tom94022 (talk) 22:26, 13 September 2009 (UTC)
Thank you for the new saying. --Sibazyun (talk) 23:04, 14 September 2009 (UTC)

Name versus scope[edit]

If this article is intended to just be about early disk drives, then the material on the 2321 Data Cell doesn't belong in it. If it is intended to be a general article on early IBM DASD, then the 3850 and half a dozen drums, e.g., 7320, 2301, 2303, need to be added and the name changed.

As a side note, there were a few abortive disk drive on the IBM 1400 and IBM 7000 series that were based on the 350 and displaced by the 1301 and 1311. Shmuel (Seymour J.) Metz Username:Chatul (talk) 22:09, 17 June 2010 (UTC)

I agree the article's name and scope are inconsistent, see 8. Scope discussion above. The 2321 should be dropped and there should be a cut off related to "early". I proposed renaming the article to IBM Mainframe Disk Drives, which is mainly what is currently covered but didn't get a lot of buy in. The cut off would be the 3390. FWIW, aren't the "abortive disk drives" the 353, and 355 discussed in the article? If not, why not add them? Tom94022 (talk) 04:16, 18 June 2010 (UTC)
I'd read 8. Scope, but it seemed to relate only to dates, not to type of DASD covered.
8. Scope points out the absence of many small disk drives which is definitely a scope issue. So what do you want to do, expand the mis-named "Early" article or rename and focus it on what it really covers that is mainframe (SLED) disk drives or ? Tom94022 (talk) 18:00, 18 June 2010 (UTC)
There's more than one scope issue; the one that I was concerned with was whether the article should cover only disk drives. If you want it to cover all types of DASD then I can give you references on, e.g., the 3850 Mass Storage system (MSS), but I don't have anything on the early drums.
The article is about Disk Drives not DASD, the question is how to we fix this article given its content exceeds its title, its scope is incomplete and the time covered is inconsistent with "early" Tom94022 (talk) 00:32, 19 June 2010 (UTC)
Removing the 2321 and adding the 7300 would address the issues that I was concerned with. As for your issue, is it possible to arrive at a consensus on what the cutoff is for early?
Perhaps the article should be split into articles covering early and later disks? Shmuel (Seymour J.) Metz Username:Chatul (talk) 02:02, 20 June 2010 (UTC)
I don't consider the 353 and 355 to be abortive; I was referring to, e.g., the 1405, the 7300. Shmuel (Seymour J.) Metz Username:Chatul (talk) 10:20, 18 June 2010 (UTC)
The 1405 is in the article. I am looking into the 7300 and will add it when done - FWIW, it appears to be a rebadged 355. Tom94022 (talk) 18:00, 18 June 2010 (UTC)
I believe that both the 1405 and 7300 were rebadged 355's, and that the announcements of the 1301 and 1311 rendered both the 1405 and 7300 noncompetitive. Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:20, 18 June 2010 (UTC)

Here is my proposal. Rename this article to:

  • IBM MAGNETIC DISK DRIVES with the following sections
  1. Early IBM Disk Drives - Every drive in the article prior to System/360 using Pugh's "IBM's Early Computers" as a basis
  2. IBM Mainframe Disk Drives - the SLEDs 2302 thru 3390
  3. IBM Small Systems Disk Drives - 2310, 5540, 62GC, 62PC, etc
  4. IBM OEM Disk Drives - needs work, links to DeskStar
  5. IBM Floppy Disk Drives - probably just a few words and a link to Floppy disks
  6. Retrospective - IBM's exit from the HDD business and a comparison between RAMAC and their last disk drive
  7. See also, etc.
  • Redirect Early_IBM_disk_storage to Section 1 of IBM MAGNETIC DISK DRIVES, as above.
  • Move IBM 2321 Data Cell to its own article

I used "Magnetic" in the article title to avoid having to add the various Optical disk drives that IBM OEM'ed from other suppliers. Comments and/or suggestions Tom94022 (talk) 19:30, 20 June 2010 (UTC)

If the title drops the word early, shouldn't the IBM Mainframe Disk Drives section of the article be expanded to include magnetic disk drives beyond the 3330, e.g., RAMAC Virtual Array (yes, they recycled the name)? Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:17, 1 July 2010 (UTC)
I don't think any subsystem or storage control unit belongs in an article with the term "disk drive" in the title. They are not in the current article and need not be in the retitled article. The topic of subsystems in general and IBM in specific is interesting and could be a separate article. You might want to take a look at the Computer History Museum's Storage Subsystems site for one approach. Tom94022 (talk) 19:04, 1 July 2010 (UTC)
Then perhaps the alternate title should be IBM disk storage. Or perhaps the article should be split into separate drive and storage articles. Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:17, 1 July 2010 (UTC)
This is a drive article as written so there is nothing to split away. All I am proposing is correct the title and expand the coverage to all IBM disk drives. The problem with IBM disk storage is both the ambiguity between devices and subsystems and the inclusion of optical. The proposed title avoids both problems. If you want to write an article on DASD subystems, that would be great. It is a different article. Tom94022 (talk) 20:26, 1 July 2010 (UTC)
OK, Please get off this site Tom. You are everywhere I go. Why must you insist you change articles? (talk) 02:37, 14 July 2010 (UTC)
  • I am taking the absence of discussion as consensus to go ahead and rename and restructure this article.
    My draft sandbox is at IBM magnetic disk drives. Right now I am struggling with organizing the disk drives of the 1980s that were both internal to IBM small systems and sometimes offered as an OEM drive. The common thread is only the internal code name, e.g. Piccolo was variously the 62PC (internal number), 0680 (OEM), 3310 (low end 370), 4963 (Series/1), 5430 (System/34), 5381 (System/38) and with the 8100 processing unit. As soon as I figure out a structure that makes sense I will finish the sandbox and then rename and reorganize this article. Any suggestions? Tom94022 (talk) 22:55, 5 April 2011 (UTC)
Not so fast. I think there is value on focusing on the early IBM drives as they pioneered modern mass storage. I would prefer a separate article on more modern IBM mass storage. System 390 might be a good dividing line.--agr (talk) 02:38, 8 April 2011 (UTC)
First of all this is not fast - the discussion was first posted almost a year ago. My work is responsive to the then posted comments.
Your System/390 proposed cut off of 1990 is not much different than my "Star" series cutoff of 1994, so it appears that your objection boils down to changing the article title. Early is rather subjective, personally I think anything prior to S/360 is early. Disk storage is broader than just magnetic disk, leaving out all optical disk. So the title needs to be changed. The proposed revisions fixes the title, adds many of the missing magnetic disk storage and cuts off when IBM switched from designing principally for its customers to designing principally for OEMs. Nothing is lost from the article and a lot of content is added. After I move the article I will redirect the current title into the subsection of the new article, Early IBM HDDs. If you have a better new title, I'd love to hear of it. If you have specific comments about the content I am proposing to add, please take a look at my sandbox; you can comment there or here. I see no reason to not go ahead - do u? Tom94022 (talk) 20:24, 11 April 2011 (UTC)

2305 as paging device of choice[edit]

I looked for but could not find any evidence to support the statement that the 2305 was the paging device "of choice" on any system. The IBM 2305 site does NOT mention this at all, but instead talks about it providing "greater data-handling power for database applications and batch processing. It was initially used on two large System/360 processors, the Model 85 and Model 195, and later used with the System/370 Model 155 and Model 165." It like most DASD was supported as a paging device under VM and other OSes but just another, albeit for a while fastest, DASD. In the absence of evidence, I suggest we strike the sentence. Tom94022 (talk) 05:39, 18 December 2010 (UTC)

Change made Tom94022 (talk) 00:32, 12 April 2011 (UTC)
A google search shows multiple references to IBM manuals referring to the 2305 as a high performance paging device. The hardware reference manuals are not the proper place to determine support or usage. Please reinstate the text. Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:21, 3 August 2011 (UTC)
I searched IBM "high performance paging device" and got nothing to support the claim; ditto for IBM "paging device." I do not dispute that at its time the 2305 was a "high performance paging device" even "the highest" but I have seen no evidence that it was "of choice" for any system. So please give some references that support such a claim. BTW, depending upon the page space the fixed head feature on the 3350 may have become a better choice. Tom94022 (talk) 17:34, 4 August 2011 (UTC)
Computer History
The fixed-head area of a 3350 was not useful for paging because access to it would be delayed by I/O to other areas of the disk. Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:59, 15 August 2011 (UTC)
It was initially used on two large System/360 processors, the Model 85 and Model 195, and later used with the System/370 Models 155/158 and Models 165/168, then on the model 3033." It was supported as a paging device under VM and other OSes for large mainframes, and was the fastest DASD.
The 2305 was also in use on the later 3081 Extended Architecture processors (announced on November 12, 1980, with the use of a re-developed microcode on its controller, the 2835.)
The 2305/2835 facility was the device of choice for paging and extra fast access to records, starting on the System 360 models 85 and 95
and continued on all large Models for System 370 and 380, well into the late 1980's.IgnacioM (talk) 21:23, 1 September 2014 (UTC)
The IBM 2305 "high performance paging device" was the choice for all large IBM mainframe systems, due to its fixed head design (having in effect zero 'seek access time'), Rotational Position Sensing (RPS), and Multiple Exposures, which allow it to minimize 'latency' and providing the requested data records in a very efficient manner.
Benchmarks show that the RPS and Multiple Request features provided an improved 16x factor to existing DASD's latency delay, and a much faster access due to zero seek time, compared to the other DASD using actuators to position the R/W heads. IgnacioM (IBM Microcoder) — Preceding unsigned comment added by IgnacioM (talkcontribs) 21:23, 1 September 2014‎ (UTC)
The SLAC 370/168's each had a 2305 for paging. I never asked about any other systems at the time, though expect that SLAC wasn't the only place using them. It might be that they were the paging device of choice on 168's, but not other systems. Gah4 (talk) 07:55, 14 August 2017 (UTC)
At the Technion we used a 2305-2 for SYS1.SYSJOBQE on a 370/165, later upgraded to a 370/168[a], and for PLPA when we converted to SVS. Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:12, 14 August 2017 (UTC)
  1. ^ Yes, I know that the sales manual said that there was no such upgrade. It's a complicated story and I only do simple things like systems programming, not tax law.

Moving this page again[edit]

The page discusses all IBM magnetic disk drives and no Optical disk drives or other DASD devices. As such the title is accurate and should not be changed to encompass all disk storage or all storage unless there is a commitment on the part of the editor to expand the article accordingly. Actually it should not have been moved peremptorily in the first place, but now that it is accurately titled I hope there will be some discussion before any move. Tom94022 (talk) 20:24, 29 July 2011 (UTC)


I had added a sentence about the 2310 being a standard feature on the 360/44, which a subsequent editor removed as being "too much information." Rethinking this, I see that the 2310 is listed under "HDDs offered only on IBM small systems," so I believe my update was relevant. Rather than just re-add it, I'd like to ask for other opinions. Peter Flass (talk) 13:13, 14 February 2012 (UTC)

I agree it's an important detail that belongs in the section.--agr (talk)
I disagree. For the most part in this article we do not mention any system model usage beyond the first to introduce an embedded HDD. The 360/44 was well after the introduction of the 2310. Furthermore it was a special scientific computer not really a part of the S/360 mainframe line so I am not sure we even need to change the section title but I suppose we should consider that. Tom94022 (talk) 23:05, 14 February 2012 (UTC)
The IBM System/360 model 44 featured a special disk drive that accepted the IBM 2315 cartridge, but formatted it differently than the IBM 2310. I added some text about this drive. 05:50, 8 March 2012 (UTC) — Preceding unsigned comment added by John Sauter (talkcontribs)
I reverted the text, see next section in this talk. I would point out that the formatting is a function of the disk controller and has little to do with the drive itself. As near as I know the S/360 M44 drive was a 2310. Tom94022 (talk) 20:02, 8 March 2012 (UTC)

S/360 M44 Disk Drive[edit]

Many disk drives were either bundled with or attached to IBM systems and we have not identified them separately as such herein. This is particularly true in the later years and on small systems. The drive used on the S/360 M44 was a 2310 so for consistency it should not be listed separately just as we do not list separately the various system usages of the 667. 669, 681, etc. Tom94022 (talk) 20:00, 8 March 2012 (UTC)

But note that the integrated drive on the System/360 model 44 formatted the cartridge in a different way than did the IBM 2310. The article includes the IBM 2302, which differed from the IBM 1302 only in formatting (according to the article). It could be argued that the IBM 2302 is particularly notable because of its use on System/360, but I could also argue that the integrated drive on the System/360 model 44 is particularly notable because it represents IBM's first use of Fixed Block Architecture on System/360. John Sauter (talk) 13:29, 10 March 2012 (UTC)
As noted above formatting is a function of the controller and the the drive; this is an article about drives. If in fact the only difference between the 2302 and 1302 is the format then we should combine the sections. Finally, if in fact the integrated drive on the System/360 model 44 is particularly notable because it represents IBM's first use of Fixed Block Architecture on System/360 then it probably belongs in the FBA article not hear. BTW didn't the 2311 on the 360/20 use FBA? Tom94022 (talk) 22:31, 11 March 2012 (UTC)
IMHO it's notable because it was the only occurrence of an integrated drive on a 360 system. Peter Flass (talk) 23:53, 11 March 2012 (UTC)
I agree it is notable, and it is so noted in the DASD section of the S/360 article. But it is still just a 2310 and therefore not suitable for listing as a separate section in this article. Tom94022 (talk) 00:41, 12 March 2012 (UTC)

didn't the 2311 on the 360/20 use FBA?[edit]

The IBM System/360 Model 20 Functional Characteristics manual is on bitsavers, and it reveals on page 62 that yes, the interface to the IBM 2311 did use a 270-byte fixed block architecture. Furthermore, the model 20 preceded the model 44, so, if you consider the model 20 a “real” System/360 then it, not the model 44, is the first use of FBA on System/360. John Sauter (talk) 04:13, 12 March 2012 (UTC)

Are u sure that every usage by IBM of a fixed block size corresponds to what IBM meant by the term "Fixed Block Architecture?" I'm not. The first disk drive, the RAMAC had a fixed block size. I don't think the phrase "Fixed Block Architecture" appears in either the S/360 M20 or M44 manuals although their data block sizes were fixed (based upon Google site search of the Bitsavers S/360 site. To the best of my recollection, the term was first introduced by IBM in the System/38 and AS400 36 (maybe S/34) as the only surviving relic of FS and it applied to all levels of memory. Furthermore I seem to recall, without much research, that it was then ECKD that introduced fixed block sizes but not the term FBA into S/390 (maybe E9000). This makes the FBA article quite wrong and IMO the usage of fixed block sizes on the S/360 M44 not notable, at least in this article. Tom94022 (talk) 18:03, 12 March 2012 (UTC)
I don't think the name that IBM marketing calls something is very relavent to this article, which focuses on the size, speed, internal organization and announcement date of the various disk drives. IBM has a definition of “fixed block architecture” which fits any drive that offers only fixed-size blocks of storage through its interface. This article doesn't seem to consider the disk drive's interface to be very important, so perhaps (by the standards of this article) it is not notable that the System/360 model 44 was the first System/360 that included a disk drive for which the count-key-data interface was not provided. John Sauter (talk) 02:12, 13 March 2012 (UTC)
I think you are confusing access method, channel and controller functions with the drive interfaces. For both the 2311 on the M20 and the 2310 on the M44 the drive interface was not natively fixed block but could support any format imposed by its controller including CKD as in fact the 2311 did on other systems. I bet if you looked at the formatted disk you would find CHR track format with DL fixed and KL=0. In other words, if you looked at a formatted track you could not tell whether it was written on a system with fixed blocks or not. So I agree by the standards of this article which is all about the drives that the 2310 on the M44 is not notable for the fixed block size imposed by the M44 controller. Tom94022 (talk) 07:10, 13 March 2012 (UTC)
Your speculation about the model 20's version of the 2311 is close but not correct. Bitsavers has an image of the field engineering manual at IBM 2311 FE Theory of Operation. It describes in detail the differences between the IBM 2311 models 11 and 12 (used of the System/360 model 20) and the model 1 (used on System/360 models 30 and higher through the IBM 2841). It turns out that the model 20 uses a special format which cannot be read by the IBM 2841. John Sauter (talk) 03:32, 14 March 2012 (UTC)

How many megabytes the first disk drive (IBM 350) stored[edit]

There is some disagreement and confusion on this, based on the edit history.

  • 06:47, 16 December 2011 – The 350 stored 5 million 6-bit characters (3.75 megabytes). (→‎IBM 350: 5*6/8=3.75. The channel word was 8 bits but the data word was 6 bits - the industry uses data bits.)
  • 02:29, 16 December 2011 – The 350 stored 5 million 7-bit (6-bits plus 1 odd parity bit) characters (about 2.75 megabytes). (→‎IBM 350: you don't count the parity (ECC) bits when you quote "gigabytes" for modern HDs; you don't count the parity bits on the 350 either)
  • 17:23, 5 March 2007 – The 350 stored 5 million 7-bit (6-bits plus 1 odd parity bit) characters (about 4.4 megabytes). (→‎IBM 350)
  • 08:01, 17 November 2006 – The 350 stored 5 million 7-bit characters (about 4.4 megabytes). (→‎IBM 350: text merged from IBM RAMAC trademark)
  • 04:57, 16 March 2006 – The 350 stored 5 million characters (about 5 megabytes). (→‎IBM 350: minor edit)
  • 16:09, 27 July 2004 – The 350 stored 5 million characters. (create) Green tickY

First we need the definition of megabyte—from the article– million bytes (106, see prefix mega-) generally for computer storage.
...and for byte—from the article– ... Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer architectures. The size of the byte has historically been hardware dependent and no definitive standards existed that mandated the size... The term byte was coined by Dr. Werner Buchholz in July 1956.

So, from that we have... the term byte is never used in the 305 RAMAC Manual of Operation, as surely the system was designed before the term was even coined. For our purposes, a character is a byte is a character. We are dealing with 6-bit bytes, which means the machine only supports upper case characters. Machines supporting lower case characters using 7-bit ASCII came along later. And now Wikipedia uses UTF-8 8-bit bytes. Now, if anyone wants to precisely compare apples and oranges (1950s vs. modern HDDs), they should compare how many bits, or megabits, or gigabits they can store.

I say, the 350 stored exactly 5 * 106 bytes. That's what Five decades of disk drive industry firsts, DISK/TREND said too. – 5 megabytesWbm1058 (talk) 02:46, 19 October 2012 (UTC)

The term byte today means 8 bits and has pretty much been so since 1964 or thereabouts. The RAMAC had 3.75 megabytes in 5 million 6 bit characters is accurate and meaningful. To say the RAMAC had 5 million bytes is to mis-inform the public. Furthermore the RAMAC had an 8th bit which like the parity bit is irrelevant to the information content of the characters stored on the RAMAC. My good friend, now deceased, Jim Porter agreed with this definition, not withstanding the error on the cited page. Tom94022 (talk) 02:58, 19 October 2012 (UTC)
Agree with Tom94022. The claim of "5 million bytes" is flatly wrong. IBM marketed it as "five million characters", the characters being six bits each, as was common on many IBM machines of the day. That's not the same as five million bytes. Jeh (talk) 18:39, 19 October 2012 (UTC)
Historicaly, a byte was a string of bits that the CPU could access as a unit; it could cross word boundary and could have an arbitrary size. Ever since the advent of the IBM S/360, the unqualified term byte has frequently been used to refer to 8 bit bytes on an 8 bit boundary, especially when refering to stroage capacity. Multiplying the capacity of the 350 by 3/4 to get a size in 8-bit bytes is meaningful, if not particularly useful. Referring to the capacity as 5 million 6-bit bytes would be meaningful, but refering to it as 5 million bytes is simply misleading. Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:39, 22 October 2012 (UTC)


This issue was raised again by a series of five edits on November 1 that added megabyte equivalents to the descriptions of the 353, 355, 1405, 1301 and 1311. I am inclined, having re-read the above discussion, to change the unit from megabytes to bits. If there is objection to that, my second choice would be to remove the megabyte descriptions. Any thoughts? John Sauter (talk) 13:30, 4 November 2016 (UTC)

The bytes/bits difference is always confusing, especially when people use MB and Mb. Recently thinking about inflation adjusted prices, $xxx (equivalent to $yyy in 2015), if we put xxx million characaters (equivalent to yyy megabytes today). People are more used to megabytes (Note that the 3330 seems to have been designed for 100 million bytes.) To further the confusion, it seems that marketers of magnetic tape (consider LTO for example) believe that bytes have four bits. Note that bit (and so also byte) has meaning in terms of hardware (something that can have two states) and in information theory (where it means something with two equal probability states). English text has about four bits of information (entropy) per character, and so compresses about 2:1. We could make it explicit: (... equivalent to xxx (8 bit) megabytes). But is that 1,000,000 byte megabytes, or 1,048,576 byte megabytes? Gah4 (talk) 19:05, 4 November 2016 (UTC)

I would avoid both the MB/Mb problem and the MiB/MB problem by spelling out the number of bits. I see that the incorrect description of the 355 has already been removed, so I would describe the 1405 model 1 as storing 60,000,000 bits. John Sauter (talk) 13:20, 5 November 2016 (UTC)

I have changed megabytes to bits as described above. John Sauter (talk) 16:54, 6 November 2016 (UTC)

RAMAC Disk Diameter[edit]

A IP and I have been ping-ponging over what set the size of the RAMAC disk to 24-inches. AFAICR, the IBM door requirement was 30-inches but even if it was 29.5-inches a constrained disk could be as large as 28.5-inches and still fit in a 29-inch cabinet so the chosen size of 24-inches shows no evidence of the cabinet size as a constraint. Furthermore there is no evidence in the many books and articles that the cabinet size was a factor in the choice of disk diameter. They started with 16-inch disks and apparently went to 24-inch to meet the 5 million character requirement. The pressure if anything was to make the diameter as small as possible for cost reasons within the constraint of meeting the capacity requirement. So this whole line within the article is TMI at most and likely wrong. I think it is best to just state the cabinet size and leave out all the rest. Tom94022 (talk) 00:25, 25 February 2013 (UTC)

Okey Dokey. But I'm not a newbie.  :-) Incidentally, I actually did do some search for a reference on the "gotta be able to get in through the door" purported requirement and I couldn't find any. I found a bunch of statements that were word-for-word the same as our original passage from this article. Initially, it looked like WP lifted from them, but ultimately I realized it was the other way around, so citing them would be a classic WP circular ref!  :-)
Please allow me to argue a bit about the idea of "TMI". I'm not sure it's a very valid criterion for non-inclusion. It's very subjective. (The phrase comes from "Pulp Fiction", as I recall.) I would expect it might apply in cases where an article is too long and needed to be whittled down, perhaps. It might be another word for "digression" or "off topic"? I don't think "TMI" would apply in this case at all. Instead, "notability" and "verifiability", and "on-topic" apply, and it fails on verifiability. "Notability", "verifiability", and "on-topic" are strong, and very emphasized as important criteria in WP directives. "TMI" doesn't have that same heft. In this particular case, if the disk size was limited by the cabinet size and the cabinet size was limited by doorway sizes, and if that was backed up by a reliable ref, then that I would argue is very notable, and even interesting, and very suited for inclusion. Calling it "TMI" is ambiguous and subjective and has an air of capriciousness. Okay, those are my thoughts on "TMI" for what they're worth. Best regards, (talk) 20:21, 28 February 2013 (UTC)

Disk drives on IBM 7030 (Stretch) - 353 versus 7303?[edit]

IBM had both a 353 and a 7303 disk drive for the 7030; the article mentions only the 353. Does anybody have information on the differences between the 353 and the 7303?

IBM (1960). IBM General Information Manual 7030 Data Processing System (pdf). IBM. p. 20[21]. D22-6513. A high-speed disk storage system consists of one IBM 7303 Disk Storage and its associated IBM 7612 Disk Synchronizer.  Unknown parameter |separator= ignored (help) Shmuel (Seymour J.) Metz Username:Chatul (talk) 15:08, 14 June 2013 (UTC)

I'll look into it, but I wonder of the whole group of 350 variants (e.g. 355, 1405, etc.) should be listed separately or within the 350 section. It may well be that they were just rebadged models with minor changes and not worthy of separate sections. This is what we do later on when one OEM model appears in many systems with various model numbers and/or feature codes. The 353 had a head per surface which was different than the 350 and its ilk, I don't know about the 7303 but because it was on Stretch my guess is it is a variant on the 353 and possibly should be combined with it. I would further guess that it was a double density 353. Will research this Tom94022 (talk) 12:55, 15 June 2013 (UTC)
@Chatul:Still looking into this; however, FWIW, the specified capacity of the 7303 at 2,097,152 64 bit words works out to about 26 MB on a 50 disk machine (the 7303 purports to use on 32 disks for data leaving the others to other purposes, 2.1*8*50/32=26.5) which suggests the 7303 is an enhanced version of a double capacity IBM 350 (only 10 million characters). This suggests the 353 was based in the single capacity 350. Given the 7030 shipped in 1961 it is likely the 353 never shipped but it may have been announced. Tom94022 (talk) 19:46, 15 January 2015 (UTC)
Another clue - the IBM September 1960 fact sheet gave the disk capacity as "more than 1,250,000 alphabetic characters." perhaps referring to the 353. Tom94022 (talk) 20:51, 15 January 2015 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────This is probably still OR, but i think the 7303s only shipped with the first 7030; they were followed and replaced by 353s. The 353s were 2.1 million words; the 7303s were likely the same but could have been about 1 million words. The facts and/or assumptions that lead me to this conclusion are:

  • My retired IBM SJ friends tell me the first Stretch system shipped with drives having "air" heads (like the 350) but all subsequent Stretch Drives shipped with "flying heads" (like the 1301/1405). The first drives were likely replaced.
  • The model number 7303 is only found in some system literature with early dates; we can find no product documentation
  • The model number 353 appears in product literature with later dates.
  • The earliest literature gives a capacity of about 1 million words, the later literature states 2.1 million 64-bit words
  • The 353 CE manual confirms it used "flying" heads like those in the 1301.
  • The "air" heads of the double capacity 350 at 7.5 MB could do about 1 million words. The "flying" heads of the 1405 at about 15 MB could do about 2 million words.
  • The Stretch drive at the Computer History Museum came from Lawrence Labs, the second 7030 installation (Nov 1961), and is badged as 353.

I need to get my IBM friends to post some of this at their RAMAC site so as to have an RS instead of my OR. Tom94022 (talk) 07:25, 16 January 2015 (UTC)

More OR, but contemperaneous documents (1961 abd 1963) indicate that the first 7030 shipped to Los Alamos had Model 353 disk storage units, so it is likely the 7303 was withdrawn in favor of the 353 before first shipment. Tom94022 (talk) 22:36, 19 May 2015 (UTC)

IBM 2314 address plugs[edit]

Moved from User talk:Tom94022

The first time I saw those I thought they were the most amazingly good idea ever. That's why I put it in. :) Jeh (talk) 08:11, 23 December 2013 (UTC)

I think they only existed in the IBM world for two generations, 2314 and 3330, but it is not clear why. I'm told the projected reliability of the original bundled 2314 was so low that they had to have a spare so the customer would always have full capacity but that then necessitated a means to match a specific pack to a specific channel address, perhaps for booting. A switch to take a drive off line is a lot cheaper than the plugs and that is what IBM did before and after. BTW, I am pretty sure the 3340 channel address of the drive was hard wired as in the 2311 even though the 3348 data module was movable. I suppose there are other situations where moving a pack and a plug is easier or preferable to dismount/mount operations. This all became moot with fixed media drives. BTW, I was involved in the design of the plugs for the Memorex 3330 equivalent - they were a pain and in my view good riddance :-) Tom94022 (talk) 18:15, 23 December 2013 (UTC)
One situation: Job "A" which needed pack 1 on address x is about done, and next up is Job "B" that needs pack 2 on the same address. A good operator could have pack 2 already spinning on the spare drive. When Job A is finished you just move the plug to the spare drive. Of course it would also be possible to point the job at a different drive address with a DD JCL command, but a lot of operators weren't trusted with such things. Jeh (talk) 04:36, 24 December 2013 (UTC)
If a drive failed but the pack was still good, the address plugs let you move the pack to another drive in the middle of the job and continue running. Of course, if the pack was damaged then this also allowed you to destroy the drive you switched it to.
Allowing an operator to change the user's JCL was an invitation to disaster. Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:07, 24 December 2013 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────Neither situation seems significant enough justify the cost and problems with address plugs.

  • Were there many JCL situations where the job required a specific volume to be at a specific address? I thought DOS and OS were a bit more sophisticated :-)
  • Since head crashes were a significant portion of disk pack drive failures moving a pack (and plug) from a failed drive really had a high probability of crashing a second drive (about 1 in 3 if I recall my statistics). There are apocryphal stories of operators destroying entire strings of drives by moving a crashed disk pack.

I really do believe address plugs were a consequence of the DASD product marketing decision to bundle 9 drives (original 2314 Model 1) on one control unit that only was capable of 8 online drive addresses. To bring the 9th drive online you had to take a drive off line and give its address to the "spare" drive - plugs solved that problem. Whether the bundling decision was to assure availability or to protect the 2311 revenue stream is another discussion. Tom94022 (talk) 22:00, 24 December 2013 (UTC)

Level of detail?[edit]

User:Tom94022 recently removed some material from the section on the IBM 2311, and that raises the question of the appropriate level of detail. In particular, should the paragraph describe the differences among the 2311-1, 2311-11 and 2311-12 and how much should it say about those differences? Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:42, 6 February 2014 (UTC)

Sounds like it should be a table. The guidelines have nothing that fits - it's not "overly detailed." A comparison of how speeds and capacities have changed over the years sounds like valuable information to me. As I recall this article has some fairly zealous editors who work to keep it on topic, but in this case I think the mateial belongs here in some fashion or other, Peter Flass (talk) 17:31, 6 February 2014 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── On yr broad question of appropriate level of detail I suggest the material needs be notable and not "overly detailed" For example:

  • The article generally does not mention A2, B2 or B1 models of IBM's later HDDs.
  • On the other hand the article goes thru the various 2314 derivatives because they are notable in context of the IBM responses to the market in the late 60s.
  • The 1311 section IMO appears to be too detailed.

Specifically with regard to the 2311-11 and 12 and I suggest saying nothing more than the 2311-11 & -12 were were variants for use on the System 360 M20, with the 2311-1 and 2311-11 field convertible and the 2311-12 a half capacity drive. A table seems too much. Tom94022 (talk) 20:14, 6 February 2014 (UTC)

Do we need three 1311 Photos[edit]

We now have three 1311 photos, two of which are essentially the same and appear distorted. I'm going to find one good color photo with a disk pack to replace the color ones unless someone objects. Tom94022 (talk) 01:19, 12 February 2014 (UTC)

Yeah, the same crossed my mind while reviewing latest edits. To me, the first one from the bottom looks most usable (though not of the best picture quality), as it also shows the disk pack. — Dsimic (talk | contribs) 02:47, 12 February 2014 (UTC)
Someone near the CHM might be able to get a better pic. Peter Flass (talk)

Most Expensive Hard Drive[edit]

Is the External Link to World's Most Expensive Hard Drive Teardown on YouTube either notable enough or reliable enough for this article? I'm pretty sure the drive is likely not the World's most expensive one, certainly not if adjusted for inflation and I recall from the last time I went through that there were several factual errors. I don't want to go through it again, and even if I did, how could I correct the factual errors? So my recommendation is to not link to it on the basis that it is neither notable nor reliable. Tom94022 (talk) 18:10, 17 February 2014 (UTC)

The title of this video is bad for sure (and obviously created as such in order to attract more views on YouTube), but the content can't be that wrong – this guy is taking apart an old-generation HDD and showing its internals, what isn't that easily available to be seen. Probably at least a few of the comments in this video are having issues (especially the comments on the HDD's read/write heads, for example), but the visual part can't be that wrong.
If we could end up with a more accurate title (containing just the exact HDD model), that would be good enough to keep the link, in my opinion, as I don't think there's a better freely available video or paper showing the internals of such old HDDs. If you disagree, please feel free to delete the link, I'm far away from being married to it. :) — Dsimic (talk | contribs) 18:45, 17 February 2014 (UTC)

RAMAC Purchase Price[edit]

The purchase price stated for the RAMAC in IBM's first HDD versus its last HDDs is actually that of the later (~1959) double density 350 Model 3 (7.5 MB) rather than that of the original Model 1 (3.75 MB). This is the price of the Model 3 in Montgomery Phister, Jr's "Data Processing Technology and Economics." It is possible that there never was a separate purchase price for the 350 Model 1 since it was originally bundled into the 305 System at a time when IBM was not necessarily selling products but only renting them. However, we do have a reliable source, in Emerson Pugh’s book “Building IBM” that the rental price of the 350 Model 1 was $650/month (out of a 305 rental price of $3,200/month). We also have from Phister that the Price:Rent ratio for the 350 Model 3 was 53 months which implies a 350 Model 1 purchase price of $31,800 $34,450. The 1956 consent decree required IBM to sell its products in addition to renting them and my recollection is that they were rigorous in establishing Rental Equivalent Selling Prices. A 53:1 ratio is consistent with IBM's practices into the 1970s. Therefore I believe such a calculation is a mathematical process and not original research but I can see when some might disagree.

If anyone has any reliable source for the Model 1 purchase price that would solve this problem; otherwise, it appears we have several choices:

  1. Go with the Model 3 purchase price, reflecting its capacity and live with the inapposite tabulation
  2. Use the estimated Model 1 purchase price, reflecting the calculation in a footnote
  3. Change the table to the Model 3 throughout

Comments and suggestions would be appreciated. Tom94022 (talk) 18:25, 24 August 2014 (UTC)

The Ballistic Research Laboratories "A THIRD SURVEY OF DOMESTIC ELECTRONIC DIGITAL COMPUTING SYSTEMS," March 1961, section on IBM 305 RAMAC (p. 314-331) is mainly about the double density 350s but does have several instances of Model 1 pricing; a $650/month rental at WE Aurora, Georgia State & Hamilton AFB and (confirming Pugh) and a $34,500 purchase price at Boeing Wichita (somewhat higher than essentially the same as the estimate above). Tom94022 (talk) 06:52, 25 August 2014 (UTC)

I would go with the $34,500 price since it is sourced and is close enough to Tom's estimate. I'd also add "($311 thousand in current dollars)." --agr (talk) 10:04, 25 August 2014 (UTC)
Sorry for the math error, but we got there anyhow. Tom94022 (talk) 19:19, 25 August 2014 (UTC)

Editing Review Requested[edit]

An IP just asserted in this article and in the Hard disk drive article that the capacity of the RAMAC was 4.4 MB (more accurately 4.375 MB) based upon a 7 bit character. The actual RAMAC was an 8 bit encoded character with a parity bit and a space bit giving 6 data bits. I've asked the IP to move the discussion to this article but so far he has not done so. He/she seems to respond to multiple editor inputs so your review of RAMAC Price and Ratio would be appreciated.

IBM Micro Drive should be included in final comparison?[edit] — Preceding unsigned comment added by (talk) 01:48, 2 March 2016 (UTC)

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As well as I remember, alphameric is the IBM term for what everyone else calls alphanumeric. Then again, shouldn't this article be titled History of IBM Direct Access Storage Devices? Gah4 (talk) 02:01, 13 February 2017 (UTC)

The term alphameric included alphabetic, numeric and some special characters.
The article currently only includes disks. An article on DASD should also include drums, e.g., 7320, 2301, 2303, and mass storage devices, e.g., 2321, 3850. Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:44, 14 February 2017 (UTC)
Yes! The 2321 Data Cell drive. "Random access tape". I never saw one in action "live". NCR had a version as well. Jeh (talk) 21:04, 14 February 2017 (UTC)
Well, the 2321 "noodle picker", like the RCA 3488 (RACE) and the NCR 353 (CRAM) used magnetic strips rather than a reel or cartridge of tape. The later IBM 3850 MSS used a pair of cartridges for each virtual 3330. Shmuel (Seymour J.) Metz Username:Chatul (talk) 18:52, 16 February 2017 (UTC)
For actual random access tape, there is DECtape. The 3850 is more like cached random access, where the whole cartridge (does it have to do both?) is written to disk, modified, then written back. Do only cylinders modified have to be written back? Gah4 (talk) 19:55, 16 February 2017 (UTC)
No, the entire cartridge is not written to disk. Pages 8 cylinders long are written to disk (staged) and written back to tape (destaged). The MSC did not write back unmodified pages. Shmuel (Seymour J.) Metz Username:Chatul (talk) 21:11, 17 February 2017 (UTC)

Isn't patent US3134097 the foundational patent, not US3503060[edit]

US Patent US3134097 , "Data Storage Machine," was filed Dec. 24, 1954, and is referenced in US3503060. It's clearly the foundational patent; why is US3503060 listed as the patent here?

Simsong (talk) 23:29, 12 August 2017 (UTC)

Short answer: No - see the fixed link.
Long answer: Both patents come from the same application but only the 3503060 patent claims disk drives and IBM cited it as such in awarding the inventors, not 3134097. Tom94022 (talk) 00:08, 13 August 2017 (UTC)

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I have fixed the two references to A26-5991-0 in bitsavers. It appears that the directory structure at bitsavers has changed. John Sauter (talk) 15:18, 5 November 2017 (UTC)

Density calc seems off[edit]

On mobile, so i cant (or dont want) to calculate myself, but the "mb/mm cubed" calc is clearly off. Most likely it should be "mb/cm cubed", but possibly it's simply crap. Please recalc, and post w correct unit. Thx. קיפודנחש (aka kipod) (talk) 20:34, 27 January 2018 (UTC)

Where is this calc - I don't find it in either the article or the talk page? Tom94022 (talk) 20:57, 27 January 2018 (UTC)
The table near the bottom has gigabyte/in**3 and megabytes/mm**3. I didn't check so carefully, but it looks like some might be wrong. Gah4 (talk) 13:25, 28 January 2018 (UTC)
It looks like the line MB/mm3 is off by a factor of 1000 which would make it MB/cm3. I'll check the math and correct the label.Tom94022 (talk) 02:23, 29 January 2018 (UTC)