Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!rutgers!seismo!mcvax!cernvax!ethz!claudio From: claudio@ethz.UUCP Newsgroups: comp.sys.amiga Subject: Re: MFM format and possible improvments Message-ID: <445@ethz.UUCP> Date: Mon, 9-Feb-87 16:48:34 EST Article-I.D.: ethz.445 Posted: Mon Feb 9 16:48:34 1987 Date-Received: Tue, 10-Feb-87 06:05:01 EST References: <8702050359.AA01021@cory.Berkeley.EDU> Reply-To: claudio@ethz.UUCP (Claudio Nieder) Organization: CS Department, ETH Zuerich, Switzerland Lines: 47 In article <8702050359.AA01021@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU.UUCP writes: > > Unfortunetly, I'm no expert on disk media and hardware. This is my >understanding: > > [ some discussion about MFM encoding ] > > Current MFM: > 11 sectors * (512+32 bytes/sector) = 5984 bytes/track. > > New method which may or may not work: > 16 sectors * (512+32 bytes/sector) = 8704 bytes/track. > > Making for a 1.25Meg floppy. > >So is it possible? If so, I'll write a trackdisk driver for the baby. > >------------------------ >Note on RLL: Can't be done on the Amiga.. it requires you to boost the >bit clock for the drive. > > -Matt Sorry Matt, but that is not possible. Although I don't know very much about MFM and other disk encodings, I can tell you for sure that you will not be able to put 8704 bytes/track on the disk. The floppy controller writes to the disk with a speed of 250000 bits/sec and the disk turns at 300 rpm which means that a track is 0.2 sec long thus (0.2*250000)=50000 bits/track and no more. So the maximum you can expect to put on a flopy is 6250 bytes/track if you use no encoding but simply put every bit as it is on the disk (which, as you explained, is impossible). 6250 bytes/sec vs. 5984 bytes/sec that's only 4.5% more, so it's probably not worth the work. -- claudio (* --------------------------------------------------------------------- Disclaimer: I'm not working for ETH-Zurich! I'm just a CS student. E-Mail: UUCP: claudio@ethz.uucp BITNET: K538912@CZHRZU1A Mail: Claudio Nieder, Kanalweg 1, CH-8610 Uster, Switzerland. --------------------------------------------------------------------- *)