Commodore PC-40 III
Commodore PC-40 III
The PC30-III has a PC40-III motherboard and is a 286 running at 12MHz. I have a 1.2M 5 1/4" (Drive 0) floppy installed and a 1.44M 3 1/2" floppy (Drive 1). The drives were confirmed working in a 486 based system and are recognized when installed in the Commodore PC30. The 486 will boot from the 5 1/4" drive with a DOS 3.1 and a DOS 6 boot disk. Transferring them into the PC30 and I get a "Disk Boot error" using the same boot disks. I have tried installing the 5 1/4 only in the PC30 but still get the same boot error. I tried the 3 1/2 only with a good boot disk - same result. I've changed the floppy cable and even installed the ISA floppy controller from the 486 system - no joy. I've even tried a 360K 5 1/4 and a 720K 3 1/2 drive in the system. I don't have a hard drive that meets the BIOS drive table settings on the PC30 or I would set up a bootable hard drive in another system and transfer it to the PC30 just to verify the system will boot to DOS. This one has me baffled.
Sorry to bring an old dead/thread back, but I was having a problem adding a floppy drive to a Commodore PC-40 III as well. I landed here in my fruitless search looking for answers and felt this was a good place to comment in case anyone else ends up in this boat.
Adding the 3.5 as a second drive worked fine as long as the cable remained straight and the Commdore 5.25 is primary drive. Trying to use a flip style cable results in drive not ready/floppy configuration errors and the like.
Back when this thing came out, most drives had 4 jumper positions to set DS0 through 3 and used straight through cabling. Using modern drives is a bit of a problem here in that they're set to DS1 and expect you to use a flipped cable to determine A: or B: The PC40-III I encountered, expects A: to be on DS2, and B: to be DS1 so flipping 0 and 1 as most systems expect, won't work here. Further, there is only one motor line on pin 16.... which should not 'flip' or move.
I ended up modifying a flippy cable to allow both drives to be set to DS1. Instead of flipping 7 wires/pins 10 through 16, only flip 3 wires 10 11 12. Then change the 5.25" to DS1 instead of DS2 and you can have either in A: or B: working properly.
I believe sometime after serial number 4500ish, Commodore revised the board to use the IBM AT/flipped cable, as the service manual suggests a revision 5 board has this scheme implemented on the floppy interface.
Only time I ever needed a logic probe to install a floppy drive!
All the best.
Stuart