STARDOS for the Commodore 64's Model 1541 Floppy Disk Drive

I recently got around to starting to back up my old Commodore C64 floppy disks. First, I needed a working floppy disk drive. I had two of them put away, an original white case 1541 which tended to overheat and suffer from alignment problems and had the push down drive latch, and a newer dark beige one with the turn handle drive latch.

I started with the newer drive, opening it up first to see if any capacitors had blown up or other parts obviously failed, and was surprised to find a little circuit board plugged into the 6502 CPU socket, with the CPU moved to the circuit board. There wasn't anything to say what the little board did, other than a label that said V1.2. I had almost completely forgotten I had installed the STARDOS disk speedup system, when I was porting my Tree Charts to the C64 (an add-on to the Quinsept Family Roots genealogy program) in fall 1987 (got an Amiga A2000 the same year, so the C64 was just for work then).

Powering up the drive seemed to work - no smoke, the power light works, the status light comes on, drive spins, then it stops. I dug out my C64 computer to test it with (happily still working), but when hooked up to the disk drive, it failed to read any disk. There was some head seeking, and disk spinning noises, but no data. I took out the modifications (there were some to the C64 too - an extra wire and a ROM cartridge), but still no luck. It's probably a failure of the disk read/write head, common for that kind of drive. The older 1541 did work, after I realised it had been set to unit number 9. Setting it back to the usual 8 got it working normally; things like games ran just fine.

I'll be updating the white 1541 to support parallel data access (kit from Peter Schepers) and get a USB adapter for it (ZoomFloppy from RETRO Innovations), so it will be able to read a whole disk in under 30 seconds, rather than 10 minutes at the original slow (400 bytes per second) serial bus to the computer speed. The STARDOS system would have run at a speed between the two, using a faster serial speed (they claim 10 times faster, but probably 2560 bytes per second). But not as fast as hard wiring 8 bits of data to unused I/O pins inside the disk drive (6000 bytes per second).

Anyway, here are a few photos of my STARDOS system, including the original tin can packaging (actually the sides are made of silvered cardboard). Also have a look at Dave64's photos and ROM dumps for yet more detail.

[Collage of STARDOS Packaging Can and Contents]

Copyright © 2020 by Alexander G. M. Smith.