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From: alan@drivax.UUCP (Alan Fargusson)
Newsgroups: net.micro,net.micro.pc
Subject: Re: Floppy Disk Formats
Message-ID: <159@drivax.UUCP>
Date: Tue, 18-Jun-85 20:51:03 EDT
Article-I.D.: drivax.159
Posted: Tue Jun 18 20:51:03 1985
Date-Received: Sun, 23-Jun-85 00:16:14 EDT
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Organization: Digital Research, Monterey, CA
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> [obligatory offering to non-existant bug]
> 
> Long, long ago, in a galaxy far, far away, there was a world which used single 
> density 8" diskettes.  Then along came better technology, and lo, there was 
> double density 8" diskettes.  But existing boot roms didn't know how to read
> double sided diskettes, so OEMs began mixing the format of their disks, using
> single desntiy for the boot tracks, and double density for the rest of the 
> disk.
> 
> So a question comes up:
> 
> In DOSland, is there a significant number of OEMs still using mixed density
> 8" disks?  For that matter, has anyone ever come across mixed density
> mini-flops?  And finally, on a slightly different subject, has anyone noticed
> any floppy formats on double sided diskettes on which the track numbering is
> other than "down the cylinder" (track 0 is on hd0, track 1 is on hd1, track 2
> is on hd0, cylinder 1, etc)?

The iNTEL 310 has this problem with 5-1/4 disks. The boot track has to be
single dinsity 128 bytes/sector. The rest of the disk can be any size except
that there is a bug that prevents 512 byte sectors from working, so we had
to put a driver on the boot track to read the UNIX kernel. It is very anoying.
The winchester drive is similar except that the boot track has to be 1024 byte
sectors. System V just doesn't work with 1024 byte sectors. Swap and physio get
confused. More anoyance. In fact the code for the 1024 byte file (FsType 2)
system was not complete until we ported it. A bit more anoyance.
-- 

Alan Fargusson.

{ ihnp4, amdahl, mot }!drivax!alan