Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!mcsun!ukc!reading!cf-cm!cybaswan!iiitsh
From: iiitsh@cybaswan.UUCP (Steve Hosgood)
Newsgroups: comp.sys.ibm.pc
Subject: I think I found how to write 360K on AT 1.2M drives
Summary: It's the BIOS - some are faulty
Message-ID: <859@cybaswan.UUCP>
Date: 9 Nov 89 16:13:12 GMT
Reply-To: iiitsh@cybaswan.UUCP (Steve Hosgood)
Organization: Institute for Industrial Information Technology
Lines: 41
References:

A while back there was a discussion along the lines of "why can some people
write 360K disks in 1.2M drives when others can't?". Even the physics of the
situation was a problem - how *can* an AT 80-track drive write the wider
tracks of a 40 track disk? People suggested that the drives may have split
heads to allow this, but this seems to be wrong. NEC for instance claim they
don't use split-head drives.

I discovered that I could write 360K reliably on *one* of our ATs at work but
not on another. Both had NEC drives, an FD1155C which wrote the 360K disks OK,
and an FD1157C which didn't. So I swapped the drives from one machine to the
other. The effect stayed with the *machines*! Now the 1157C wrote 360K disks
and the 1155C didn't. So I swapped the controllers. Still the effect stayed
with the machines!

I started to suspect the BIOS. The machine that could write 360K disks had a
CAC-AMI (?) BIOS, the other had an AWARD 3.01. I discovered another machine
in our office had an AWARD 3.03, so I swapped BIOS ROMs over.

The fault vanished! I then discovered that the machine with the AWARD 3.03
had been able to write 360K disk all along, using a TEAC FD556FR drive,
so it definately seems that with the right BIOS, just about any drive can
write 360K.

So scrap your AWARD 3.01 and get something better! Is 3.03 the latest, or
has anyone seen a 3.04? There is still a bug in AWARD 3.03, in that
the soft reset doesn't work properly. If you use RAMDRIVE it gets left in
limbo by the CTL-ALT-DEL sequence, and doesn't come back up. Hard reset
works OK (on RAMDRIVE 1.19 anyway).

Does anyone know a fix for this problem please?.

Steve
iiitsh@pyr.swan.ac.uk


PS:
I have not found out how to write 720K 5.25" disks in an AT drive yet. I
believe it may not be possible. The media description byte on 720K disks is
$FB, which is the same as 1.2M disks. I suspect this confusion means that
an AT will use the wrong write current to try and write to a 720K disk.
Any comments anyone? Is the guy who wrote FDFORMAT listening?