On Friday 07 June 2013 09:04:36 Martin Gregorie did opine:
Some time back my 68000-based OS/9 system died and I needed to get stuff off the 3.5" floppies I use to back it up.
I'm a Linux user, so I used setfdprm to fiddle with the parameters in the 'floppy' driver and was able to image the disks successfully and then use the os9exec OS/9 emulator to access their contents.
The reason I'm mentioning this is that I used a standard Linux driver, which normally uses 512b blocks and a standard 3.5" drive to read OS/9 floppies while the parameters needed to read the OS/9 floppies were:
hd sect=34 ssize=256 head=2 cyl=80 tracksize=8704 dtr=0 zerobased
I haven't yet tried it on any Flex-09 disks: mine all use single density for track zero and deduce the format of the other tracks from its contents. I wrote the drivers and may have diddled with the formatter when I replaced the original two disk FD card with a Windrush card that that handles 4 drives off a pair of FDC chips.
I'm posting this to say thanks for writing such a good "get out of jail free" utility and as an indication to any other Linux users of just what setfdprm is capable of.
Martin
I don't want to rain on this parade, but there are FDC's on some motherboards that flat will not access disks other than 512 byte/sector.
The board in this box is one such. Doing a setfdparm to the 256 byte format that the 6809 os9 machines use, and then sending dd to either read or write a disk image will churn and hammer the drive for several retry cycles, then apparently tosses the dice to see if it locks this quad core phenom up, requiring a hardware reset or returns an error. If a write was attempted, I can take the disk to a real os9 system and inspect it with dEd, and it has not been touched. This is an ASUS M2N-SLI Deluxe board I paid nearly 300 USD for, not too long after the phenoms came out.
The moral I guess is that if you need to access 256 byte per sector disks, make sure the FDC on the board you are buying will indeed work before dropping the card for it.
Cheers, Gene