More PS/2 trouble

[zorori]

I did get my Model 70 to "mostly work" by attaching a spare 720K FDD from my PS/2 Model 30. It worked, although I had to make special 720K versions of the reference disk. I'd like to be able to attach some sort of 1.44MB FDD to the system, but I'll settle with what I can get working for now.

I measured the resistance and DC voltage (approximation) for each pin on my stupid hand-made 40-pin to 34-pin adapter cable. Compared it to a reference system where the FDDs work. There seems to be no problem from these simple measurements. Don't tell me that I have to hook up a logic analyzer and capture traces.

Guess I'll also PM the guy who wrote the comment about making sure that the FDD is "jumpered" to work as Drive B, to see what he meant. Hopefully he's still around. He said it was "super important", so maybe this is the info I'm missing.

 

[modem7]

Guess I'll also PM the guy who wrote the comment about making sure that the FDD is "jumpered" to work as Drive B, to see what he meant. Hopefully he's still around. He said it was "super important", so maybe this is the info I'm missing.

That no doubt is a reference to setting the drive to the second 'drive select' setting. So if DS0/DS1/DS2/DS3 are available, choose DS1. If D1/D2/D3/D4 are available, select D2.
If the drive access light is turning on at times as expected, then the setting is correct.

 

[zorori]

That no doubt is a reference to setting the drive to the second 'drive select' setting. So if DS0/DS1/DS2/DS3 are available, choose DS1. If D1/D2/D3/D4 are available, select D2.
If the drive access light is turning on at times as expected, then the setting is correct.

Thank you. Well, then the setting is correct. Drat, I was hoping that was the problem, since I don't know what else it could be.

 

[modem7]

http://ohlandl.ipv7.net/floppy/floppy.html goes into the differences in 2.88M drives. I used it in attempt to get a particular PS/2 2.88M drive going in a late AT clone (with 2.88 support in BIOS and controller). The document gives you an idea of the subtle differences between systems/drives. 1.44M drives are less complex, but still, the document contains "With the 1.44Mb PS/2 floppy drives IBM moved one ground and one unused pin to put the 5 & 12VDC power on the 34-pin connector. By my references they seem to have inverted a half-dozen control signals too". Inverted signals might be part of your problem.

 

[IBMMuseum]

http://ohlandl.ipv7.net/floppy/floppy.html goes into the differences in 2.88M drives. I used it in attempt to get a particular PS/2 2.88M drive going in a late AT clone (with 2.88 support in BIOS and controller). The document gives you an idea of the subtle differences between systems/drives. 1.44M drives are less complex, but still, the document contains "With the 1.44Mb PS/2 floppy drives IBM moved one ground and one unused pin to put the 5 & 12VDC power on the 34-pin connector. By my references they seem to have inverted a half-dozen control signals too". Inverted signals might be part of your problem.

The quote is actually from me, probably over ten years ago. I was running in circles, with Louis prodding me on. Gave up on the straight cable solutions, and went with reverse engineering on aftermarket external floppy drives for the PS/2s, with several chips (ultimately my goal was for standard 1.44Mb drives to work on the IBM systems).