whitney@husc4.HARVARD.EDU (glen whitney) (07/31/87)
I own an AT-compatible with a 1.2Mb high density drive. FASTBACK manages to write 720K to a standard diskette (double density) in one of these drives by using 80 tracks. I would like to know if this is possible through DOS. Any help would be appreciated, as this would cut my disk consumption in half. Wayne Whitney -- whitney@husc4.harvard.edu (ARPANET) whitney@husc4.UUCP (UUCP) ..!harvard!husc4!whitney (also UUCP) 72770,2020 (CIS) "You can't fight in here, this is the War Room!"
hundt@wind.bellcore.com (tom hundt) (08/04/87)
Sounds to me like the 1.2M drive is half-stepping... I seem to recall
that this thing has 160 tracks...? That would explain 720k.
Anyone got an installable driver to do this? Sounds like a great
idea (albeit fostering yet more incompatibility).
/-^-\ Thomas M. Hundt / BELLCORE Morristown NJ / hundt@bellcore.bellcore.com
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/--_--\ brown@nicmad.UUCP (Mr. Video) (08/05/87)
In article <1802@bellcore.bellcore.com> hundt@wind.UUCP (tom hundt) writes:
<Sounds to me like the 1.2M drive is half-stepping... I seem to recall
<that this thing has 160 tracks...? That would explain 720k.
<Anyone got an installable driver to do this? Sounds like a great
<idea (albeit fostering yet more incompatibility).
A 1.2Mb floppy drive is a 96tpi drive, with 80 usable tracks, spinning at
a higher rate (360 vs 300) to achieve the higher data storage. A 720Kb
5.25" floppy is a 96 tpi drive running at the normal rate.
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terminus-/ BITNET: brown%nicmad.UUCP@spool.wisc.edumjg@ecsvax.UUCP (Michael Gingell) (08/05/87)
It is possible to make a 1.2 meg drive write 720 k on standard disks. A 1.2 Meg drive is 80 track double sided and is normally controlled by your AT's BIOS to write in high density 80 track (1.2 Meg mode) or in low density 40 track (360K) mode. In 360k mode the drive double steps. To get 720k in low density you have to have an additional software driver that does more or less the same code as for 360k except that the double stepping is eliminated and a new disk parameter block specifying this format must be selected while accessing this format. To do all the above you have to have a software driver resident in RAM which intercepts the Disk I/O INT 13H or 40H and checks to see ]if this is a 720k request for a sector read write or format, if so it must handle the call itself else pass it to the regular BIOS handler. Any volunteers to write the code for this ? Mike Gingell ....decvax!mcnc!ecsvax!mjg