|2040/3040/4040||Dual Drive||Single Sided||Single Density||170K||IEEE-488|
|2031/2031LP||Single Drive||Single Sided||Single Density||170K||IEEE-488|
|8050||Dual Drive||Single Sided||Quad Density||521K||IEEE-488|
|8250/8250LP||Dual Drive||Double Sided||Quad Density||1042K||IEEE-488|
|SFD-1001||Single Drive||Double Sided||Quad Density||1042K||IEEE-488|
|1540/1541/1541II||Single Drive||Single Sided||Single Density||170K||IEC|
|1570||Single Drive||Single Sided||Single Density||170K||IEC|
|1571||Single Drive||Double Sided||Single Density||340K||IEC|
As you can see, quite a variety of single and double drive, single and double sided, single and quad density. Drives with the same capacity were generally compatible with each other for reading, but not writing. Double sided drives could read single sided disks, but you still had to flip them over if you had used both sides in a single sided drive. So it's often difficult to work out what drive a disk was written in. When I was looking for a working drive for my PET, I found a scan of a German Commodore 64 magazine from the 1980s which had an article about converting a 1541 disk drive into a 2031 clone. (Update, it was 64'er magazine, see the last entry on this page at zimmers.net) Narrowing it down, you can see the 2031 and 1541 have similar specifications, other than the connection type.
|Drive||No. Drives||No. Sides||Media Density||Capacity||Connection|
|2031||Single Drive||Single Sided||Single Density||170K||IEEE-488|
|1541||Single Drive||Single Sided||Single Density||170K||IEC|
The 2031 used parallel IEEE-488, the 1541 used the serial version of the same protocol. 1541's were the most common disk drive used with the Commodore 64, and VIC20, so there are a lot of them around, unlike the 2031 and the other IEEE-488 drives. The 2031 originally came in a large black metal case, using the same drive mechanisms as the 4040 drives. Later the 2031-LP was produced, using the case and drive mechanism from a 1541. Since the schematics of the 1541 and 2031-LP were very similar, the idea was to take a 1541 drive and modify it to match the 2031-LP schematic. The ROM would be replaced with the 2031 ROM (actually a patched ROM to make the 1541 act like a 2031). All the changes were to the IO pins of one of the 6522 chips, so this could be achieved with an add on board which connected one of the 6522's to some IEEE-488 buffers rather than the IEC ports on the drive.
real 2031LP from xAD nIGHTFALL) Just needs a label for the front. I was going to copy a 2031LP label, but the drive cases I used has the embossed C= logo, so it wouldn't fit.
The PCBs are available from my Tindie store. The most difficult parts to locate are the IEEE-488 connections. You can try to find something similar to the arrangement I used above, or solder a cable directly and run a long lead to an edge connector on the PET.
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