> From: owner-cc65@musoftware.de [mailto:owner-cc65@musoftware.de] On Behalf > Of Fatih Aygün <snip> > >Atari. There's no good method to quickly determine the number of sectors > on > >a disk. :) > > > I believe there is: > > 1 - Read the 4th sector. (the xf551 drive had a bug, it returned the wrong > PERCOM info after reading the normally 128-byte boot sectors, a read from > sector 4 eliminates this chance) > > 2 - Read status (SIO command 0x53) and save that info. > > 3 - Request a PERCOM block. If it succeeds use that information. > > 4 - If reading PERCOM block fails assume 1050, 810 (or even 815) or > compatible. Use the status byte 0 to differentiate between single, > enhanced (medium) and double density. (bit 5 is set if double density and > bit 7 is set if enhanced density). If we're only looking for sector count, > only the bit 7 matters. This is a good solution, didn't think of the status command! I can think of at least a few scenarios where this wouldn't work (devices that don't support Percom block that aren't 1050 or 810 disk drives-for instance early MyIDE), but I don't think that would be very many. ---------------------------------------------------------------------- To unsubscribe from the list send mail to majordomo@musoftware.de with the string "unsubscribe cc65" in the body(!) of the mail.Received on Thu Oct 25 08:48:14 2012
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