umbirch2@ccu.umanitoba.ca (Robert Birch) (11/06/89)
Can someone please send me code on how to change the sync of the amiga
drive? I would prefer the code to be in assembler. Also could you include
sample code on how to change it and how to access the drive using it?
Thanks
<umbirch2@ccu.umanitoba.ca>
Robert Birchccplumb@rose.waterloo.edu (Colin Plumb) (11/09/89)
In article <1989Nov5.234511.12776@ccu.umanitoba.ca> umbirch2@ccu.umanitoba.ca (Robert Birch) writes: > Can someone please send me code on how to change the sync of the amiga > drive? I would prefer the code to be in assembler. Also could you include > sample code on how to change it and how to access the drive using it? Um... I'm not sure what you mean. The low-level disk format that includes the A1 sync marks the Amiga floppies use is the sole and exclusive property of the trackdisk.device, so unless you want to use some disgusting hack modifying the trackdisk.device code, you have to reimplement the trackdisk.device. This is a non-trivial amount of work. But because it's hidden inside the trackdisk.device, I'm not sure why you'd *want* to change it. If you could give me some information about the perceived need, maybe I could give you better information. One useful source for this (although it has got a number of disgusting hacks I don't encourage using) is Abacus' "Amiga Disk Drives Inside and Out." Note in particular that their floppy accelerator could fail on some Amigas. As C-A has said, while it is true that some floppy drives can step at 1.5ms, much less than the rated 3ms, others will fail at 2.8ms or before. Also, if you're playing with longer tracks, you should know that the Amiga's bit clock is actually 2.5% fast of 2us/bit, but you have to allow 2% (I think) for motor speed variation and 5% (I think) for Amiga clock variation due to genlocks. It may work on your machine, but follow the specs if you want it to work on others... -- -Colin