[EMAIL PROTECTED] ha escrito: > Antonio Rodr?guez <[EMAIL PROTECTED]> wrote: > > Almost all Apple II computers use the 800 Kb disk format, which is > > propetary of Apple, and can not be read/written without specially modified > > drives. > > My understanding is that the problem is with the drive controller, not the > drive itself.
The problem is not only the disk controller (of course, it uses a different schema of low-level encoding, GCR versus MFM), but also with the drive itself. In Apple IIs and Macs, DD 3.5" disks achieve a 800 Kb capacity where the same disks only get to 720 Kb on the PC because Apple stores more data on the outer (and longer) tracks. This is achieved by rotating the disk at different speeds depending of the track you're reading or writting (slower in the outer tracks, faster in the inner tracks), because disk controllers allways transfer data at a fixed bitrate (500 kbit/second for 3.5" drives, IIRC). Standard PC drives are completely unable to control they rotation speed. Of course, there are special 3.5" drives for the PC that are capable of reading Macintosh/Apple II 800 Kb disks, but AFAIK they are more difficult to find than the equivalent solutions for the Apple II line (3.5" drives capable of reading PC disks). The fact that 3.5" drives started to become popular in the PC about as the same time as Apple presented its PC-compatible SuperDrive doesn't help much, either (in fact, the PC was one of the last platforms to adopt the 3.5" format, but I'm disgressing). > Anyhow, never say never. Somebody has managed to get Apple II 5.25" > diskettes to "work" on a PC floppy drive. See the comp.sys.apple2 FAQs, > part 7, question 7. That's a different problem. Apple II 5.25" disks use a different low-level encoding, yes, but they rotate at a constant speed, so they don't need special disk drives. In the times when the Apple II and the PC were the two main brands of computers, there were special disk controllers for the PC that let you read Apple II disks using a standard PC 5.25" drive by implementing in hardware the low-level encoding used in the Apple II. Modern computers have enough speed to do this in software while "cheating" on the disk PC's controller (which is a lot more complicated than Woz's Disk ][ controller and doesn't directly allow low-level bit-wise access to the disk drive). But as I said before, the differential rotating speed doesn't allow to do this in a 3.5" drive, or at least make it a lot more difficult. Maybe someone would find a way into it, but I think it's rather unlikely - remember we're talking about using *standard* PC hardware. Greetings, Antonio Rodr�guez (Grijan) <ftp://grijan.cjb.net:21000/> -- Apple2list is sponsored by <http://lowendmac.com/> and... / Buy books, CDs, videos, and more from Amazon.com \ / <http://www.amazon.com/exec/obidos/redirect-home/lowendmac> \ Support Low End Mac <http://lowendmac.com/lists/support.html> Apple2list info: <http://lowendmac.com/lists/apple2.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/apple2list%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
