Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!mcvax!ukc!etive!djm From: djm@etive.ed.ac.uk (D Murphy) Newsgroups: comp.sys.ibm.pc Subject: Re: 1.2meg/360k compatibility question Message-ID: <2575@etive.ed.ac.uk> Date: 17 Jul 89 15:15:34 GMT References: <561@amms4.UUCP> Reply-To: djm@etive.ed.ac.uk (D Murphy) Organization: Edinburgh University Chemistry Lines: 43 In article <561@amms4.UUCP> hjg@amms4.UUCP (Harry Gross) writes: >> >In the case of the 720K vs. 1.44M drives, no such problem exists. The data >tracks are the same size on both drives. The only difference is whether or not >data is recorded on one side, or both sides. Thus, a good mix of floppy drives >would be 1 each: > > 360K drive (probably as drive A) > 1.2M drive (probably as drive B) > 1.44M drive (what ever you wish - D? E?, etc., but probably > NOT C) > >Hope this helps > >-- > Harry Gross | reserved for > | something really >Internet: hjg@amms4.UUCP (we're working on registering)| clever - any >UUCP: {jyacc, rna, bklyncis}!amms4!hjg | suggestion Umm - this ain't true. 720K 3.5" drives are formatted 80 tracks/side, 9 sectors/track and use both sides. 1.44M disks use 18 sectors/track, but have the same track width. This is according to the IBM manual *and* the MS Programmers reference. I also know its true cos I wrote a program to replicate some wierd sector formatting using this as a basis and it worked. The head addressed in the read/write operation is one of the parameters in the BIOS call (13h, I think), and you also pass this when writing directly to the FDC. I have a 720K as a second floppy on my PC, and trying to get it to format to 1.44M by writing direct to the FDC doesn't work - presumably the old NEC controller couldn't address 18 sectors because it only has an 8 bit sector address register. Incidentally - even if it were true it wouldn't matter because you can't just turn a 3.5" disk over to use the other side like you could with a 5.25" - there is a diagonal cut-out in the top right-hand corner which stops it being put in the wrong way, and the hub is only exposed on one side. Murff.... JANET: djm@uk.ac.ed.etive Internet: djm%ed.etive@nsfnet-relay.ac.uk Murff@uk.ac.ed.emas-a Murff%ed.emas-a@nsfnet-relay.ac.uk trinity@uk.ac.ed.cs.tardis trinity%ed.cs.tardis@nsfnet-relay.ac.uk D.J. Murphy *Artificial* intelligence ? Evidently.....