5.25" floppy drive bible ?

[Chuck(G)]

Great, thanks for the pointers, i downloaded the pdf, and i'm almost sure its a ds-qd drive, i'll put up to my 5160 test setup and see for sure, the stepper motor label has 1.875 degree step rate faintly visible on it. Isn't that the step rate for a 1.2mb drive?

It depends. I don't know about your 9428, but some manufacturers double and quadruple (e.g. Micropolis) stepped to improve positioning accuracy.

 

[k2x4b524[]

It is indeed a 720kb 5.25", in my xt tester, it would only double step as the bios on my test board is an older one, this symptom shows up in my 720kb 3.5" formatting as 360 unless drivparm is used. but drivparm doesn't work on this 9428 either, however when the 9428 is plugged into my pentium machine, or even my win 7 machine, it reads as a 720kb drive and formats as such. Strange huh, there is even a jumper to set it for double or single steps.
I'm sure all 4 are 720kb now though. That pdf saved my bacon.