User talk:Tom94022

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History of the double sided floppy drive[edit]

Tom,

Here is some interesting history on the development of the double sided floppy drive.

I Googled for - shugart sa450 1976

Start reading around page 170

In the Matter of "Certain Double-Sided Floppy Disk Drives and Components Thereof"
Investigation No. 337-TA-215
USITC Publication 1860
May 1986
United States International Trade Commission, Washington DC

-- SWTPC6800 (talk) 02:56, 13 April 2008 (UTC)

Assistance requested with ATA SSD issue[edit]

Hi, I wonder if you have a moment to give a third editor's opinion? I and editor Ramu50 are in a dispute on the AT Attachment page over whether solid state disks are supported under ATA. The issue is pretty well summarized in an [[1]] I opened at reliable sources noticeboard. Ramu50 continues to remove the reference to solid state drives from the article lede, even though there is a citation supporting it. If you have a moment I'd appreciate your opinion, either in the form of assisting to revert what I consider vandalism to AT Attachment or comments on the talk page. (Sadly, admins have taken no action on my request to revert that page's recent rename.) Jeh (talk) 07:35, 18 July 2008 (UTC)

Thank you for your response there. It was very helpful as it made me realize that the issue of "support" is irrelevant. Re SSD the article lede simply says that ATA is used to connect them, and this is true (there are obviously many such products on the market) whether or not they are "supported". (In fact afaik there is no actual claim of "support" for anything anywhere within the ATA/ATAPI documents; they are merely descriptive. True? Jeh (talk) 23:31, 21 July 2008 (UTC)
Exactly, the specification is a description of a standard, the sellers of products assert they comport to the standard. I don't think anyone would say that NTSC supports TV's. If yr TV meets the standard it works in the US at least now, but it doesn't work in Europe (SECAM, I think) :-) Tom94022 (talk) 05:29, 22 July 2008 (UTC)


Shugart or Seagate. Associates or Technology[edit]

It seems to me that the SA drives are Shugart Associates, and the ST are Seagate Technology. Was there an in-between time that was Shugart Technology?

Note that the ST506/ST412 manual in the references was published as Seagate Technology.

Gah4 (talk) 01:36, 21 November 2008 (UTC)

Yes, Seagate Technology was originally named Shugart Technology. The very first ST506 drives had a Shugart Technology technical data plate. The ST412 was much later in time. The name Seagate was chosen so the ST remained the same. Go to http://www.computerhistory.org/search/ and search "Shugart Technology" if u don't believe me. Also you can look for an Al Shugart speech where he went thru the whole story. Tom94022 (talk) 20:32, 21 November 2008 (UTC)

14" HDD[edit]

See Early IBM disk storage#IBM 1311. Edward (talk) 22:21, 31 December 2008 (UTC)

Yes I am well aware of drives having (14" and 24") disks but there never was any agreement as to size, mounting holes and connector style and location which is what I think we mean today when we talk about form factor. To the best of my knowledge no two 14" disk drives had the same size. Tom94022 (talk) 04:45, 2 January 2009 (UTC)
Actually there was some standardizaion of form factor when 14-inch drives moved into ASME rack mounting as with Diablo cartridge and CDC SMD drives, both of which used 14-inch disks. To the best of my knowledge the 2311 and 2314 class of drives were packaged in boxes with no standardard form factor. Tom94022 (talk) 19:10, 16 April 2017 (UTC)

Shugart and Conner in 1978[edit]

"With all due respect," I think you overstepped your mission in deleting almost all of the entry I edited last week declaring it "incorrect and too much information," and did so again when I rentered only my part of that entry (because I agreed the rest was TMI), but I challenge your statement that it was incorrect. In fact technically it is now incorrect, requiring a reader to view the footnote to get the true fact, which I'd say is an inconvenience at best. The fact is the company was founded as Shugart Technology and was no more than an office over a strip mall in Scotts Valley when I met there with Finis Conner in 1980 (construction for its building between the mall and the freeway broke ground shortly after I was there; I returned a few months later and saw the building complete, and by then the name was Seagate). If you think the TMI content preceding my first edit was incorrect, you should check it out before saying so - Al Shugart was an IBM employee before founding/co-founding SA and ST, and Finis, his cofounder at ST, was a former Memorex employee. If you had read the reference I inserted you would've known Al met Finis at Memorex in 1978. And any bio on Al says he left IBM in 1969. 01:33, 20 April 2010 (UTC) —Preceding unsigned comment added by 74.198.12.14 (talk)

For this chart about the current HDD companies, I think the fact that the name was originally Shugart Technology is TMI and should be in the Seagate Technology article, not here.
I did read the reference you cited and it is not a reliable source. Neither Alan Shugart nor Finis Conner were employees of Memorex in 1978. According to multiple reliable sources Shugart left Memorex to found Shugart Associates in 1973. According to multiple reliable sources Finis had left Shugart Associates in early 1978 for IMI and then with Al incorporated Shugart Technologies on Nov 1, 1978. It is not likely they ever met "at Memorex" in 1978. BTW, it is likely they first met at Memorex in 1969 (or maybe 1970) when we (Al, Finis and I) were all working together. Tom94022 (talk) 05:06, 20 April 2010 (UTC)

To sum up the above they worked together at Memorex prior to 1978 (when they met to discuss the subsequent founding of ST later that year) - they had attracted engineers from IBM to Memorex and hence to SA, thus the founders were ex-employees of both IBM and Memorex. Ergo, the entry deleted as "incorrect" was correct. 08:26, 20 April 2010 (UTC) —Preceding unsigned comment added by 74.198.12.14 (talk)

Neither Mahon nor Mitchell ever worked for IBM or Memorex; therefore the group was not "ex-IBM and ex-Memorex" or even "ex-IBM or ex-Memorex". Tom94022 (talk) 21:21, 20 April 2010 (UTC)

You're playing that old "semantics game" simply for the sake of argument. (You assume that the original entry included the word "exclusively," which it didn't, to my recollection.) 01:42, 21 April 2010 (UTC) —Preceding unsigned comment added by 74.198.12.14 (talk)

No games, just trying to eliminate misleading information. Here is the original quote:

1979: Seagate Technology is founded by a group of ex-IBM and ex-Memorex personnel.

Here is the employment history of the five founders:
founder last employer next last next last next last
Shugart unemployed Shugart Assoc Memorex IBM
Conner IMI Shugart Assoc Memorex
Iftikar Memorex
Mahon Shugart Assoc Diablo Xerox
Mitchell Commodore Bendix Fairchild
IMO I don't see how this group can accurately be described as "ex-IBM and ex-Memorex", particularly since only one person had worked at IBM, 10 years and 3 jobs previously. It also is TMI, so I took it out. Tom94022 (talk) 00:15, 24 April 2010 (UTC)

Thanks for the info - it seems to me you've proven the essential veracity of the TMI content with 60% of the founders (including both of the major players) meeting at least one of the dual criteria. I suspect the original author thought of the former colleagues of those 3, who brought their expertise from Memorex and IBM to SA and hence to ST, as part of the "groups," making it even more valid, despite the decade elapsed. (Remember that I have agreed that it was TMI for this section but it wasn't incorrect in that the word "exclusively" was not used - thus it becomes simply a matter of semantics.) 74.198.12.14 (talk) 01:05, 26 April 2010 (UTC)

Low level formatting and stepper-servo[edit]

Buh? Why did you remove all the material on steppers and servos from the LLF article? None of that material is "specific to the IBM PC" as you commented at the time but was used by everyone in the industry across all manufacturers. The whole LLF section is basically devoid of content without those sections. As such I am in the process of reverting/restoring your content removal in July. DMahalko (talk) 18:33, 26 November 2010 (UTC)

All disk drives have low level formatting and it has nothing to do with the actuator mechanism. We low-level formatted when we had hydraulic actuators, open loop voice coil motors and external closed loop voice coil motors long before we had stepper and servos. Most of the material was specific to "PCs" and other small computers and ignored or was incorrect when one looks at the entire history. Tom94022 (talk) 20:08, 26 November 2010 (UTC)
So I went back and looked at the edit - at the time the stepper motor became widely used in the HDD industry it was principally used on IBM PC and compatibles (and of course Apple), the rest of the industry used, had been using and continued to use track following servos well into the 1990s. So the whole section was very specific to PCs of which IBM and its clones dominated the market. Most of what I removed was only accurate in context of IBM PCs and clones, e.g., did u use the BIOS to format an IBM S/360 disk pack? Go ahead and try to improve the article but please keep in mind that low level formatting goes back to the first commercial HDD. Tom94022 (talk) 20:21, 26 November 2010 (UTC)
  • I reverted most of your material since yr distinction between mainframe and PC HDDs is without substance. Note that the ubiquitous 512 byte sector common to all computer system markets came from the PC market. The history about RLL vs MFM really applies to all disk drives, the controller and the drive had to have compatible specs. The same thing happened with earlier drives, it just wasn't as public. FWIW, I did try to add some of your content. Tom94022 (talk) 18:18, 27 November 2010 (UTC)

As well as I know it, 512 byte disk sectors were popular long before the IBM PC. The first computer system I remember them from is HP_Time-Shared_BASIC, but they were also popular on DEC systems like PDP-11 and VAX. The PDP-10 uses 576 byte sectors, or 128 of its 36 bit words, so a little more than 512. Seems to me that just about everyone except IBM's CKD used 512 or similar disk block sizes. Gah4 (talk) 05:30, 14 September 2015 (UTC)

Most if not all subsystems other than IBM mainframe CKD and its compatibles used fixed sector sizes for HDDs and FDDs (even IBM used fixed sector sizes before and after CKD) and it is highly likely someone used 512 byte sectors before the IBM/XT, but it was the success of the PC with its 512 byte size that made it ubiquitous. Tom94022 (talk) 06:02, 14 September 2015 (UTC)
As far as I know, all VAX disks are 512 byte sectors. (VAX paging uses 512 byte pages, way too small.) If the PC didn't put DEC out of business, then 512 byte DEC disks might have become ubiquitous. People were already making 512 byte sector disks, and so those were used for the PC. (Pre-PC floppy controllers could do 128, 256, 512, and usually 1024 bytes/sector.) It would seem that were computers with keyboards existed before the PC, but the PC made them ubiquitous. But the most important distinction is byte addressability, which is pretty much due to IBM and S/360. Otherwise, power of two multiples of some other word size might have become more popular. Gah4 (talk) 18:33, 14 September 2015 (UTC)
You can't be serious about keyboards in general but I could make a similar observation about the PC keyboard layout becoming ubiquitous. There is no doubt that some DEC HDDs had 512 byte sectors (particularly PDP11) but DEC had other block sizes on DEC systems so I wouldn't call the block size ubiquitous for DEC. BTW, it all depends upon the controller not the system. I am pretty sure that some of the HDD controllers for VAX used a physical sector larger than 512 so as to accommodate other DEC architectures such as the 36 bit PDP10 (36*16=576). A VAX logical block size of 512 would be written to the larger physical block. Most pre-PCs controllers (such as the ones u cite) could do a variety of block sizes including non-binary but soon after the PC/XT they defaulted to 512 and then with SCSI and IDE there wasn't much choice for a long time (yes I know some have 520 byte block options). Why do you think the SCSI and IDE committees picked 512? Tom94022 (talk) 19:29, 14 September 2015 (UTC)
Well, I wasn't trying to be too serious about keyboards, but it seemed about as obvious as disks. Yes the non-eight-bit-byte DEC machines used other sizes, but the world was converging on 8 bit bytes for S/360. Now, if intel hadn't made the 8080 but instead the 6060 or 9090, things might have been different. But once 8 bits caught on, 512 was likely PC or not. I suppose some possibility of 256 (many 5.25in floppys were 256 byte sectors, and 128 was popular for 8 in, from the IBM standard). As well as I know it, the DEC controllers can't choose. The PDP-10 controllers read/write 576, the VAX read/write 512, so tape if you want to cross between them. (The only one I actually know is RP-06.) The IBM floppy standard stores log2(N) in the sector header, so only allows for powers of two. Not so obvious is 256, 512, or 1024 would have won without the PC, but 512 seems more likely. VAX was pretty popular, though maybe overpriced, for some years, and DEC killed the 36 bit line. MicroVAX would have expanded 512 byte sectors to the low end without the PC. I am not sure what Apple might have done. As I remember the early SCSI drives, you could set the sector size and ask for a low-level format. The drive, in an hour or two, would format to that size. After not so long, only 512 or 520. I am not sure by now what sector size was used for SMD disks on Suns, but 512 or 520 seem likely. Sun also started using SCSI fairly early, though some were an ESDI drive with adaptor in the box. Gah4 (talk) 22:30, 14 September 2015 (UTC)
I agree that a 2n Byte capacity per sector in the range of 128 to 2048 was likely for a byte oriented architecture but until the PC/XT took off it seems like different systems picked different sizes. I suspect the most likely size was 256 which was sort of standard on many FDD controllers. FWIW the ST-506 and the ST-412 formatted capacity was specified by Shugart with 256 KB sectors not 512; it was the Xebec controller used in the PC/XT which established 512 as the standard for a formatted ST-412 that every one then followed. I'm pretty sure it was chosen because it yielded 512 more data bytes per track (that is a very non-binary 17 sectors per track). Tom94022 (talk) 05:21, 15 September 2015 (UTC)

As for stepper motor, it does seem that was IBM. I remember a seek speed test program, run on an IBM (real) AT, and said something like "this drive is so slow, are you sure it isn't a floppy drive?" That was when I had a fast voice-coil Miniscribe 6053 at home.Gah4 (talk) 22:35, 14 September 2015 (UTC)

AFAIK IBM never made a stepper motor HDD; it did buy a bunch. In the late 1970s most HDD manufacturers were pushing areal density thru track following. There was an early stepper motor HDD by 3M in very limited volume but the breakthrough to low cost HDDs using stepper motors was first the Shugart SA4000 (14-inch), followed almost immediately by the SA1000 (8-inch) and then the ST-506, the latter imitated by many, Miniscribe included. Tom94022 (talk) 05:21, 15 September 2015 (UTC)
OK, 256 or 512, could have gone either way. I think 256 is best for 64K address space machines, where smaller buffers have an advantage, and 512 for larger machines, such as VAX and later PCs, but I might not be sure everyone else would figure that out. Note, though, the advantage of CKD: one can optimize the block size for the available machine memory, and in addition it is much easier to do locate mode I/O. Small 360's used 80 byte blocks, along with 8K to 64K core. One trades off efficient disk usage for efficient core usage. For larger machines, block size gets larger, disk usage is more efficient, and also I/O transfer is more efficient. As I noted before, the 512 byte page size of VAX was too small almost as soon as VAX was released, but that might have kept the 512 byte disk blocks around longer than they should have been. I now wonder, if the early PC had gone with 256, and not so much later it was found to be too small, they might have gone to 1024 or 2048, which are probably better choices for modern systems. (Well, who knows what current disks do inside.) But between VAX and Sun, I think 512 would have been pretty popular for some years. Gah4 (talk) 07:20, 15 September 2015 (UTC)

History of hard disk drives[edit]

I was not able to find any document suggesting Samsung had entered the worldwide HDD market in 1988. Would you be able to provide any reference?g2g886 (talk) 08:04, 19 April 2011 (UTC)

The cited reference (Disk/Trend 1989) gives the date of first shipment to a customer of the Samsung 3.5-inch 40 MB SHD2041 as fourth quarter 1988. This is sufficient, but if you want additional confirmation how about:
  • A later Electronic News article dated Oct 21, 1991, notes that "Samsung initially approached the market with a 3.5-inch 40MB ..." which "was never very competitive ..."
  • The 1988 Disk/Trend published before 4Q88 does not list any shipment date for the product.
Enuf? Tom94022 (talk) 16:20, 20 April 2011 (UTC)

HP 7935[edit]

I have some firsthand knowledge of the device having built them as a student intern in the early 80s on the assembly line. I took a rather tiny article and expanded it - it still could use some good fleshing out though. HP called it the BFD for at the tome they thought the capacity rather large. It was a staple on HP3000 & 9000 minicomputers. Not the most landmark device but was notable for a number of reasons. Mikebar (talk) 01:06, 15 December 2011 (UTC)

I noted a lopsidedness with the history article you might care to comment on. Not a personal comment but one on the article as a whole. Mikebar (talk) 01:40, 15 December 2011 (UTC)

Floppy disks[edit]

Hi Tom, re my edits at floppy disk: The floppy disk drive indeed connects as a USB drive, as you said in your revert summary; but the article now says that the floppies themselves are used as an external drive, which doesn't make sense. Hence why I changed it to "could be used with an external USB drive", since you need the additional piece of hardware (USB FDD) to access floppies.

If you were thinking along the lines of "they are considered by the computer to be an external drive", in my experience USB floppy drives show up as drive A, so for all intents and purposes they are no different to an internal FDD. — This, that and the other (talk) 01:42, 20 November 2013 (UTC)

Sorry but there is no fixed relationship in Windows between drive letters and a designation of a drive as "external" or "internal". Anything connected by USB is regarded as "external," regardless of the drive letter assigned. An external device is treated quite differently from an internal, in many ways. It is not "for all intents and purposes no different from an internal FDD." Jeh (talk) 06:26, 20 November 2013 (UTC)
Perhaps we have an interesting semantics issue - are we confusing internal/external a physical attribute with removable/non-removable (or mountable or ...) an OS attribute. I am not aware (maybe ignorant) of any Windows attribute such as internal/external and when I used to have them my external SCSI drives were treated by Windows the same as my internal IDE drives (different drivers of course) except in the case of SyQuest which was external but removable. BTW, at one time I had an internal removable SyQuest too. I believe Windows designates all USB drives as removable whether they are SSD, HDD, optical or FDD and of course they are external because they plug into a USB socket which is to the best of my knowledge always a connection to the outside. Also note the recent introduction of eSATA, removable in Windows or not? Tom94022 (talk) 17:29, 20 November 2013 (UTC)
Hmm, USB (and FireWire) are not always connections to the outside! since motherboards do have USB, and sometimes FireWire, headers that can connect to e.g. a flash card reader that's mounted "internally" in a 3.5 or 5.25 bay.
It is true that "external" is not one of the "exposed" (if you know where to look) properties of devices in Windows, but it is an assumption of various bus drivers. USB is assumed to connect to external devices, ATA is not. This leads to setting some of the other device capabilities, which are exposed. The device capability most closely associated with this is indeed "removable." There is also "warm eject supported," meaning that the drivers support physical removal of the hardware, and of the device from the OS's device tree, while the system and the device are powered up and running, and "surprise remove OK", which means that even though "removable" the device won't show up in the "safely remove hardware" applet. "Removable" is implicit for anything on USB and FireWire - this is set in the drivers for their respective host controllers, and propagates to all of their child devices. SCSI is normally regarded as not removable because the usual drivers have no way to know if a particular SCSI device is on a physical interface where a hot disconnect can be done without electrical problems (SCA vs. old SCSI-1). SAS and SATA normally default to removable, but the OS turns this off for the drive containing your boot partition. In all cases, a device-specific driver, or a filter driver, or a bus filter driver can change what the bus driver decides. For example, if a mobo has an eSATA port it would be possible for the drivers that come with the mobo to add a filter driver to the SATA stack that would set the eSATA port "removable" but the others not. This would require knowledge in that filter driver of which port number was the eSATA port. But that would preclude people from effectively using hot-swap internally-mounted SATA bays. Jeh (talk) 19:14, 20 November 2013 (UTC)
It is complicated. I should have said mostly external, the best real world example of an internal USB device is an internal USB Floppy Disk Drive available from several sources but I am not sure there are too many of them. I guess they come with a mobo header to USB cable. FWIW, I wouldn't count flash card readers as USB devices because for the most part they do not use the USB connector. Tom94022 (talk) 07:36, 21 November 2013 (UTC)
Open up Device manager, find one of the flash card readers (under "Disk drives", right click, select Properties. Details tab, hardware IDs. See all the PnP IDs that start with USBSTOR? Right. The operating system, the USB host controller driver, the USB host interface chip, and finally the driver for devices in the USB storage class, most certainly see them as USB devices! If the devices on the ends of the cable are "speaking" the USB protocol, and the signaling is electrically compatible with the USB specs, it's a USB device, even if the only "cable" is a set of traces running from one point on a PCB to another. The connector has nothing to do with it. Jeh (talk) 08:56, 21 November 2013 (UTC)
As I said, "I wouldn't count flash card readers as USB devices because for the most part they do not use the USB connector." They are Memory Cards, Flash Cards and that's how they are presented to the public. Only a few such are identified as USB and they use a USB connector. The internal OS support is IMO academic. Tom94022 (talk) 16:26, 21 November 2013 (UTC)
With very rare exceptions the flash card reader does have a USB connector. That's how it connects to the computer. The only way I can make sense of your claim is to assume that you're conflating the flash card itself with the reader. It is true that flash cards themselves (SD, CF, etc.) are not USB devices. (In fact a CF card is, as you know, a parallel ATA device!) But a flash card reader is, these days, almost always a USB device, specifically a USB mass storage device with its media removed. (Note that media removability and device removability are two very different things; all four combinations are possible.) When you put a flash card in a reader, the whole is a USB mass storage device with media present. Even on notebooks with e.g. built-in SD slots you'll find these devices use USB internally. A USB storage "key" is of course a USB mass storage device (removable) with non-removable media.
"With very rare exceptions": There are CF adapters for PCcard slots that are essentially just plug adapters; they take advantage of the PATA compatibility feature of those slots. No USB in that path. Conversely, though, every smart card reader I've tried that plugs directly into a ExpressCard actually uses USB internally: There's a "USB mode" in that slot, sort of similar to the "ATA mode" of the PCcard slot, except that it permits connection to a lot more different devices. Jeh (talk) 18:49, 21 November 2013 (UTC)
An external memory card reader probably has a USB connector so it is external not internal; I am not going to bother researching bulkhead mounted readers but 1) I suspect they have headers to connect to the mobo and not a USB connector and 2) they are by far the higher volume. BTW, to be very clear, by USB connector I mean a connector approved under one of the USB standards. Probably the best example is a PS/2 keyboard plugs into a PS/2 connector while a USB keyboard plugs into a USB port and, yes an adapter can change a PS/2 keyboard into a USB keyboard. The internal attachment and software layers is academic; the physical connector is part of the identity, at least that's how most of the world sees it. Tom94022 (talk) 20:55, 21 November 2013 (UTC)
I see. That's one way to look at things. The way I (and device manufacturers, and driver writers) look at it, the headers on the mobo are USB connectors. Says so in the mobo manual, and on the mobo itself. And they do have an industry standard pinout. If we paid attention to what "most of the world" knows or doesn't know we would still be in the dark ages. Tell me: if it's not USB, then what is it? If it's not USB, then disabling the USB host controller driver won't keep it from working.. right? Jeh (talk) 21:42, 21 November 2013 (UTC)
Thanks for seeing it one way. I really don't think the Memory Card manufacturers advertise their devices as USB Memory Cards (except for a very few) nor do their customers think of them that way. On the subject of "dark ages" if we paid attention to what a few think then we wouldn't teach evolution in the schools. Of course if you pull out any layer in a layered OS the device will stop working; that doesn't mean a layer names the device only that it is accessed thru that layer. Let me give u one more example, I have a monitor with both DVI and HDMI connectors, depending upon my graphics card and the cable it can be accessed as either, but try as I can, I cannot find such a named driver in my Windows stack. And it happens another such monitor is connected thru a DVI cable to a DVI connector on a port replicator which in turn is connected to the system thru a USB cable and thus supported by the USB stack in part - I don't think anyone, even most driver developers would call such a monitor a USB device - do you? Tom94022 (talk) 08:01, 25 November 2013 (UTC)
Sorry for beating an obviously dead horse, but it's that the card readers are USB devices, and memory cards aren't. See this listing for yourself, "USB" is clearly noted there, and NewEgg.com is all but an academic site. :) On the other hand, memory cards are Secure Digital, Compact Flash etc. types of devices; that's how they interface with the rest of a computer system (or an embedded device), and that's how they're named and marketed. — Dsimic (talk) 02:53, 3 January 2014 (UTC)
The card reader has a USB port but that doesn't make it a USB device nor is it so represented by Newegg unlike this one of many Newegg USB FDDs. Its all semantics :-) Tom94022 (talk) 03:42, 3 January 2014 (UTC)


Format filler values[edit]

Hi Tom, I am looking for an explanation for the choice of a particular format filler value by various manufacturers and thought that you might know the answer.

For example, 8.0" (CP/M) floppy diskettes came pre-formatted with a filler value of E5h. (Since Tim Paterson took advantage of this fact, when he implemented the FAT12 file system for 86-DOS, this had and still has some interesting consequences for a number of odd implementation details of all FAT file systems up to the present.) But why were 8.0" floppies pre-formatted with E5h in the first place?

Another example: In all original IBM PCs since 1981 (and most compatible computers), freshly formatted floppies (and harddisks) are filled with a filler value of F6h. In IBM compatibles this value is stored in the Disk Parameter Table (INT 1Eh) by the BIOS and formatting tools (or formatting routines inside the BIOS) retrieve it from there during formatting. It can be changed easily to other values (and some clone manufacturers actually changed it to other values), but the question remains, why did IBM choose the value F6h, originally? What's special about it?

(Atari seems to have used E5h also on 5.25" and 3.5" floppies under GEM (probably by way of Digital Research), and Amstrad seems to have used F4h instead of F6h in some of their IBM PC compatible machines. On ROM and flash drives (which aren't actually formatted), the filler value often defaults to FFh in order to reduce wear, while on many modern hard disks it is 00h, if they are formatted by tools not adhering to INT 1Eh.)

Basically, these format filler values are "don't care" today, but I am trying to track down their origin and find out the technical reason for them. What I know for sure is that these values weren't a choice of random originally. I very vaguely remember having read somewhere (probably in the late 1980s or early 1990s), that this was down to FM/MFM properties or disk controller hardware peculiarities and seem to remember that these values represented bitpatterns particularly "good" to distinguish originally. But I am not sure about it any more and cannot remember the source.

Do you, perhaps, know the answer (or remember other format filler values by some vendors)?

Thanks and greetings --Matthiaspaul (talk) 13:28, 22 April 2014 (UTC)

(talk page stalker) Excellent question, looking forward to tracking down the origins of those values! — Dsimic (talk | contribs) 14:40, 22 April 2014 (UTC)
(talk page stalker) That's perhaps related to the way DOS performs an optional verification after a floppy is formatted, so it first writes those values and reads/compares them later? Probably the filler value was selected so it's a bit pattern that "stresses out" well the properties of a magnetic media. See also the explanation of FDISK.EXE's behavior. — Dsimic (talk | contribs) 14:56, 22 April 2014 (UTC)
To the best of my recollection they were driven by two things. First was an attempt to at least stress test the medium by using a challenging pattern (apprroaching worst case) and the second was to avoid a media defect in the data field looking like an address mark which was usually all zeros with one or more dropped clocks. The second criteria eliminates 00h (but it does raise the question of what happens when the user or system fills with all zeros). As I recall in MFM the worst case pattern in DB6h (an isolated zero as in ...1101 1011 0110 1101 10...); E5h and F4h are pretty much the same thing and approach worst case, F6h is closer. Some might argue that E5h/F4h are better because they have all three frequencies (1F, 1.5F and 2F) while the worst case and F6 have only two frequencies (1F and 2F) but I don't think that matters. I suspect the programmers being lazy didn't want to deal with a three hex character repeating field in a binary world :-) Tom94022 (talk) 06:59, 23 April 2014 (UTC)
Thanks for your answer. Much appreciated! So, the selection of a particular value really seems to have been down to encoding/modulation properties, perhaps with some remaining level of freedom to choose from a small range of more or less equally "good" values. However, if there was some level of freedom involved, why did all manufacturers of 8-inch floppy diskettes use the same value? Was there any kind of standard defining this? --Matthiaspaul (talk) 23:24, 23 April 2014 (UTC)
Sorry for the small delay - I missed yr question. FWIW, the 8-inch industry was much smaller and IBM was the clear technology and product leader. Every media manufacturer needed to assure compatibility of their disks with IBM hardware so I suspect caution led them to format their media exactly as IBM did - if it ain't broke don't "improve" it mentality. That is, IBM was the defacto standard. I could ask around if a less vague answer is important. Tom94022 (talk) 17:00, 25 July 2014 (UTC)
Well even more, it was usual for 8 inch floppies to come performatted. Maybe it was that drives weren't (yet) good enough to do it. I always thought that DEC sold preformatted floppies, so that they could charge more. When 5.25in floppies came out, there wasn't so much of a standard in place, many systems used their own specific format, and it was usual to sell them unformatted. (Or what was left after the last pass of testing.) As the IBM PC got popular enough, it became more usual to sell them with that format for convenience. Many DEC systems can't do low-level formatting, but could do high-level (writing the file system blocks). The latter was often INIT. By the time of 3.5in, both PC and Macintosh were popular, and they came formatted in one of those formats. Also, using preformatted 8 inch floppies, it was usual to do sector interleave with a look-up table. With 5.25 in, where the low level format was done by the user, it was more usual to write the sector headers with the appropriate interleave values. Some floppy controllers allow one to specify the fill byte, others don't. Gah4 (talk) 23:19, 17 April 2017 (UTC)

IBM "core drive"?[edit]

I seem to remember that IBM had, for the s/360 line, a sort of a "core drive": A box with a MB or so of slow core in it, with a selector channel interface. It acted like a 1 MB very fast disk drive. Do you recall the model number? Jeh (talk) 23:26, 22 July 2014 (UTC)

You may be thinking about the IBM 2361 LCS which to the best of my recollection was memory bus attached and used a memory interface and not the DASD interface. The S/360 M65 Functional Characteristics Manual sort of shows this. The 2314 Airlines Buffer feature was a disk cache but not separately addressable. I think the STK 4305 was the first "Solid State Disk" for an IBM Mainframe but it was S/370 era. Tom94022 (talk) 06:12, 23 July 2014 (UTC)
Thanks! Jeh (talk) 09:58, 23 July 2014 (UTC)

For outstanding contributions[edit]

A Barnstar!
The Computing Barnstar

Tom94022 is hereby awarded this Computing Barnstar for DataVault and other outstanding contributions that have dramatically improved Wikipedia's coverage of how the bits are stored. – Margin1522 (talk) 20:08, 17 January 2015 (UTC)

RS for Command Retry[edit]

I updated my response to your query by including two links documenting Command Retry, both in the same manual:

Command Retry is signaled by the combination of a unit check and status modifier. Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:52, 6 December 2015 (UTC)

False information and fake references[edit]

I didn't have time to post this the other night but here goes.

You have been caught providing false claims to a Wikipedia article. When asked for a reference, you then invented a fake reference to support it.

With this edit you added a claim that Maxtor had aquired Conner peripherals for $6 million. When asked for a supporting reference, you provided this reference. When someone else objected you restored it with a claim in the edit summary, "Rvt nonsense, a simple Google search works", once again expecting others to properly reference your edits for you.

Your edit summary was more accurate than you had intended. Searching the New York Times for July 1990 revealed that Maxtor's aquisition was not mentioned anywhere in that month (or indeed Maxtor at all). A wider search into April turned up the aquisition story and further revealed that you made up the $6 million purchase price (which did seem to be ridiculously cheap). It was actually $40 million, thus what you restored was nonsense.

You cannot add material that you guess at or is what you recall. Further when asked for a reference, you must not just invent a reference to cover your false claims. That is a path to an indefinite block for WP:NOTHERE.

It is now necessary to scrutinise all your past edits and delete all that are not adequately referenced on the grounds that you are an editor who has an established history of adding false material, adding false souces and misrepresenting those sources that you do use. --Elektrik Fanne 12:24, 4 May 2016 (UTC)

--Elektrik Fanne obviously didn't look very hard. A simple Google search of "ny times miniscribe july 1990" gets to.
Company News; Maxtor Acquires Miniscribe Assets, NY Times, July 3, 1990
I used the 4+2=6 million dollars Maxtor paid to creditors instead of the $46 million Maxtor apparently paid in total, including btw $30 million of injected captial. So at best we have a disagreement about meaning of the terms but the accusations of "false claims" and "fake references" are slander. And the subsequent reversions of edits as "Unreferenced. Edit from editor with history of making 'facts' up" is without merit and is arguably edit waring.
Why am I not surprised that --Elektrik Fanne has been blocked indefinitely from Wikipedia. Tom94022 (talk) 01:35, 8 March 2017 (UTC)

September 2017[edit]

Notice of No Original Research Noticeboard discussion[edit]

Information icon There is currently a discussion at Wikipedia:No original research/Noticeboard regarding an issue with which you may have been involved. Thank you. Fountains of Bryn Mawr (talk) 01:19, 12 September 2017 (UTC)

Notice of noticeboard discussion[edit]

Information icon There is currently a discussion at Wikipedia:Administrators' noticeboard regarding an issue with which you may have been involved. The thread is "Proposed topic ban for Tom94022". Thank you. --Guy Macon (talk) 22:29, 27 September 2017 (UTC)

BTW, thank you for your contributions to Wikipedia[edit]

Yes, honestly. As some of our interests are similar, I've often noticed your works on WP, and appreciated them. Though we've recently run into differences on Disk storage, that doesn't affect my opinion of your contributions. I just thought I'd put that out now, as saying anything similar after the "data" issue is settled (either way) might come off sounding less genuine, and I do want us to work together in the future. 'Later. --A D Monroe III(talk) 19:00, 28 October 2017 (UTC)

ArbCom 2017 election voter message[edit]

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