Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!brl-adm!rutgers!ames!ucbcad!ucbvax!fizbin.DEC.COM!binder From: binder@fizbin.DEC.COM (Sold - but we have others) Newsgroups: comp.sys.apple Subject: Re: IBM/Apple disk interchange? Message-ID: <8701022246.AA16363@decwrl.dec.com> Date: Fri, 2-Jan-87 16:51:00 EST Article-I.D.: decwrl.8701022246.AA16363 Posted: Fri Jan 2 16:51:00 1987 Date-Received: Fri, 2-Jan-87 21:36:43 EST Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 28 Query from TMPLee@dockmaster.arpa: > Does anyone know of any software that would run on an Apple II and allow it > to read and/or write IBM PC format (5.25") disks (with a regular Apple > drive) or which would run on an IBM PC and allow it to read and/or write > Apple-formatted disks? (I'm talking about software, not a hardware card, > for instance.) (either Apple DOS or ProDOS format) Seems like it ought to be > possible on the Apple since the Apple drive is driven at a very low-level by > the 6502. Nope. Can't be done. IBM's disks are written and read by an industry- standard disk control chip that will do either FM (double frequency) or MFM (Miller Code) and nothing else. The chip requires an Index signal from the drive once per revolution; recording is synchronized to that Index pulse during the formatting operation. The Apple's controller is equally restricted - its custom state machine can't do anything except the special GCR (group- coded recording) that Woz invented to make it so cheap. And the Apple drive, also cheapified, does not provide an Index signal, because it's not needed - Woz used self-synchronizing preamble formats. The low-level control by the Apple's 6502 consists of handling spinup/down, stepper motor sequencing, and so on - there's no direct access between the read/write path and the 6502. Cheers, Dick Binder (The Stainless Steel Rat) DEC Enet: ASD::BINDER UUCP: { decvax, allegra, ucbvax... }!decwrl!asd.dec.com!binder ARPA: binder%asd.DEC@decwrl.ARPA