Reply 20 of 38, by Deunan
Vendest wrote on 2023-10-17, 13:41:After booting into DOS, it gives an error "General failure reading drive B"
Did the drive spin up and try to read the floppy at all? I'm assuming that with not ready error it happens pretty much right away?
If so that would mean the drive is indeed locked to 360rpm and will work as 1.2M but not as 360k. It will read and write (with the usual caveat of narrower head) 360k floppies set as 1.2M but this is done via a software trick that all PC floppy controllers implement (by using 300kbps signalling rate instead of 250kbps). But that trick will not be used if the drive is set to 360k since it should then natively run at 300rpm and not need it.
It would also mean the RDY is output on pin 34 instead a DC signal and it trips DOS. This can perhaps be tested. You can't read or write an actual 360k floppy but you should be able to format and then read a floppy on that particular drive:
- set the drive to 360k in BIOS, no seek on boot
- use 1.2M HD floppy for this experiment as the drive will be single-stepping and you need media capable of high density 80 tracks
- use format /u command
- if DOS refuses to format the floppy (usually saying track 0 is bad) then erase the floppy first with a permanent magnet, especially the outer tracks
- if there are problems don't give up right away, try a few times, weak magnet or too strong one can leave behind magnetic domains that will not easily overwrite
- ignore bad sectors if there's only a few, this is just for testing
Note such floppy will be ureadable in other drives, you can only test it on this one, and if you want to reformat it back to PC specs you should use the magnet again.