|WikiProject Computing||(Rated Start-class)|
- 1 Better photo needed
- 2 Confirmation needed
- 3 Locking mechanisms
- 4 1571 from nowhere?
- 5 Slow Bit-Banged Serial vs Fast Shift Register Serial
- 6 Head misalignment: source needed
- 7 Successor products
- 8 The drive head misalignment issue
- 9 Original research tag
- 10 BAM acronym is wrong
- 11 Rotation speed, track-to-track speed, serial speeds, DMA?
Better photo needed
This article is in dire need of a better, in focus photo. I may still have a (VIC-20 off-white color) old model in the attic collection, along with the latch and flip door beiges, so I'll try to take a couple photos or unified "stack" photo soon. -- Todd Vierling 03:46, 17 Jun 2005 (UTC)
- Or, if I beat you to it, I'll do it. :-) --Wernher 15:56, 30 November 2005 (UTC)
I just wrote the following in the section on The serial interface: To ensure a ready supply of inexpensive cabling for its home computer peripherals, Commodore chose standard DIN connectors for the serial interface. I'm quite sure I read this sometime, somewhere, but I'll need to check it again. I think the decision was made when they developed the VIC-20. If someone knows more about this, feel free to comment. --Wernher 15:56, 30 November 2005 (UTC)
-- I believe this is covered in the first chapter of COMPUTE's First Book of VIC. --CurtisP 17:09, 24 November 2006 (UTC)
- I can still recall cracking open the case and soldering points on the circuit board to change drive letters in order to add more than one drive to a system.
- What drive letters ? You mean drive number, right ?
Description of Image:Commodore64 fdd1541 front.jpg, emphasis mine
- Front view of the most common version of the Commodore 1541 disk drive, with open disk slot. This version uses a Newtronics drive mechanism, and the rotating lever is used to hold the disk in place. Note that the small toggle switch in the lower right corner is an aftermarket addition.
Description of Image:Commodore 1541-II.jpg, emphasis mine:
- Commodore 1541-II, the second of two upgraded versions of the CBM 1541 (the first upgrade was the 1541C). The 1541-II has the more modern 'radial handle' locking mechanism.
What is the difference between a radial handle and a rotating lever? boffy_b 23:13, 22 August 2006 (UTC)
- I think they are the same thing - 'more modern', as opposed to to the 'push down - release pop-out' type in the early 1541. Personally, I thought all the brown 1541 models had that earlier type of release (but it seems that I am wrong). I briefly had a 1541C that had the rotating latch, which I thougt was new to the 1541 range at the time. Jason404 (talk) 14:53, 18 October 2008 (UTC)
1571 from nowhere?
The followin paragraph starts talking about the 1571-drive, but no introduction to this drive has been made in the text.. "For compatibility and ease of implementation, the 1571's Double Sided format of one logical disk side with 70 tracks later was created by putting together the 35 physical tracks on each of the physical sides rather than using two times 40 (or e.g. 38) tracks, even though there were no more quality problems with the mechanisms of those drives. The 1571 CP/M format, however, uses the full 360 KB avaiable on that two R/W head drive."
Slow Bit-Banged Serial vs Fast Shift Register Serial
The second paragraph under the heading The serial computer interface reads:
Because a Commodore engineer at the production site took out two traces from the final drawing of the C64's motherboard, thinking they were redundant, the disk drive transferred data at a tenth of the speed it had initially been designed to handle (see "On The Edge, the rise and fall of Commodore" by Brian Bagnall, for more details).
I believe this is incorrect. The Vic-20 also suffers from the slow speed of the serial bus. I remember reading this is due to the 650X processor having to do manual bit-banging of the serial interface to read out a byte. The VIA chip has a hardware shift register which was originally supposed to be used which would have been much faster as the CPU would be free to do other things until the VIA had read in a full byte but unfortunately there was a bug in the silicon which prevented it from working properly. The VIA chip was also used in the Commodore PET computers for sound generation and the bug in these machines meant sound needed to be turned off (disable the shift register) otherwise I/O operations (on a different parallel interface) would glitch. --220.127.116.11 01:39, 26 September 2006 (UTC)
- Yes. The definitive reference is the IEEE Spectrum article (Commodore 64 should have a link to it). It was a deliberate design decision (in retrospect a poor one) to try to maintain compatibility with the 1540. (In fact, though, it wasn't compatible with the 1540!) Mirror Vax 06:29, 26 September 2006 (UTC)
Head misalignment: source needed
The following paragraph needs a published source before it can be added to the article. The fix was described to me by a repair technician in the mid-1980s. Then I used it to repair my own 1541 when it finally would not hold its alignment. The fix worked perfectly, so I know the paragraph is factual, but I don't know if it was ever published.
Although a technician could realign the head, the head drive capstan was held to its motor shaft by a swage fitting that could loosen over time, eventually making realignment futile. Future misalignments could be virtually eliminated by drilling a hole diagonally into the top of the capstan and through the motor shaft, and then driving a snug-fitting pin into the hole.
I feel that this information reveals an important underlying cause for the issue, which users tended to blame entirely on copy protection.
Mwbrooks 00:03, 2 December 2006 (UTC)
You know, I wonder if the alignment issue with these drives is really such a big problem ... Dirty drive heads can also cause problems (and this is more easily fixed with a quick clean) but people tend to claim the drive needs re-aligning first because so much has been made of that issue. 18.104.22.168 (talk) 09:51, 31 October 2009 (UTC)
- Yes, the head alignment was a big issue. Early drives seldom outlasted their warranty period before they refused to read and write disks.22.214.171.124 (talk) 18:09, 29 November 2010 (UTC)
The Commodore 1570 was an upgraded 1541 for use with the Commodore 128, available in Europe.
Actually that sounds quite "1541-POV" to me. Technically, the 1570 was not an upgraded 1541 but a downgraded 1571. The 1570's originally should have been 1571's, except for that CBM didn't have enough heads and cases (and possibly other stuff) produced (or shipped) in time so the second heads of the would-be 1571's were replaced by the 1541-style dummy head, the DOS altered so that it wouldn't try to use it, and the whole thing packed into 1541-C cases with a new sticker on. Apart from the MFM capability mentioned in the text, just like "real" 1571s, the 1570 can run at 2 Mhz.
Anybody object if I change the text accordingly as soon as I bother? Cheers, Edwing 07:47, 21 April 2007 (UTC)
- Go on ahead, as you seem to know something about it that others do not. Jason404 (talk) 17:03, 23 November 2007 (UTC)
- The temporary nature of the 1570 was given away by the sticker being a simple paper sticker rather than the more normal printed metal label. Also, it wasn't the heads that were different, it was the complete drive as the 1570 used the same Alps drive that the earlier 1541s used. One might have suspected that they were surplus stock from the earlier 1541s but the drives were different in that they contained a track zero sensor (and thus immune from the misalignment issue.) 126.96.36.199 (talk) 18:15, 29 November 2010 (UTC)
The drive head misalignment issue
Original research tag
I have removed the original research tag because whoever placed it failed to provide any clue as to what they considered to be original research either in the article or here. If anyone believes that the article does contain original research, then by all means restore the tag, but at least provide some sort of clue, either by identifying the problem with [original research?] or detailing it here. 188.8.131.52 (talk) 16:28, 18 October 2012 (UTC)
BAM acronym is wrong
This error occurs on this page, and several other Commodore-related pages. And they all link to a seperate page Block allocation map. I think this page, the mentioned page, and the several other Commodore-related pages all need to be fixed. Specifically, BAM stands for Block Availability Map (not Block Allocation Map). References include:
- 1541 User's Guide (CBM, Septemper 1982, p.9): "...[DOS] organizes them into a Block Availability Map, or BAM, and a directory."
- 1571 User's Guide (CBM, August 1985, p.23): "The VALIDATE command recalculates the Block Availability Map (BAM) of the current diskette..."
- 1581 User's Guide (CBM, 1987, p.34): "The COLLECT command recalculates the Block Availability Map (BAM) of the current diskette..."
I believe the reason Commodore calls it an availability map is because the set bits in the BAM indicate which blocks are available (opposite of allocated), and the sum of the available bits is stored in a seperate field to indicate the total number of available blocks of each track. I also believe the wrong acronymn became popular because of one of the two commands that DOS makes available to manipulate the BAM, namely Block-Allocate (the other is Block-Free). Regardless of my beliefs, Commodore is consistant and clear about the definition of BAM.
Because there have been no objections, I've added an article Block availability map and updated links in Commodore DOS and Commodore 1541 to point to it. I also updated the erroneous Block allocation map with a link to Block Availability Map, and added a link to BAM. Hydradix (talk) 06:51, 5 February 2013 (UTC)