On Sun, 8 Apr 2018, Bill Gunshannon via cctalk wrote:
I do have to admit that I find it hard to believe that the cable to the
floppy can actually make a difference.
A minor point, . . .
On 5150/5160/5170, the SECOND drive is a straight cable, FIRST drive is
crossed. Thus, drive A: is at the end of the cable, B: is in the middle
of the cable.
The P112 manual
https://661.org/p112/files/p112-doc.pdf Page 10
calls for the reverse, with FIRST drive before the twist, SECOND drive
after the twist.
IF that is correct, then your first drie is straight through. That also
means that an unkeyed cable can be reversed, as one more to try.
Termination is rarely an issue with 3.5 inch drives, and not usually the
problem with 5.25". 5.25" has explicit provision for termination, but
wrong termination usually results in slightly less reliability, not often
a total failure to read.
I did not see any mention of the disk format.
If it is 512 bytes per sector MFM, with sequential sector numbering, then
even USB drives should work for making disks.
A different sector size, or even numbering sectors from 0, would be
problematic for some USB drives.