S100 Floppy Controller Question
M H Stein
dm561 at torfree.net
Tue Nov 13 00:13:48 CST 2007
Date: Sun, 11 Nov 2007 17:51:09 -0500
From: Allison <ajp166 at bellatlantic.net>
Subject: Re: S100 Floppy Controller Question
To: cctech at classiccmp.org
Message-ID: <0JRD004G7656LL73 at vms044.mailsrvcs.net>
Content-Type: text/plain; charset=iso-8859-1
>Subject: Re: S100 Floppy Controller Question
> From: M H Stein <dm561 at torfree.net>
> Date: Sun, 11 Nov 2007 17:33:20 -0500
> To: "'cctalk at classiccmp.org'" <cctalk at classiccmp.org>
>I think Tim's point was that if your controller's smart enough to deal with a
>relatively modern 8" drive like a TM848 it could probably deal equally
>well with a 5.25" HD drive and you could transparently restore an 8" image
>(if you have one) to the 5.25" disk. The controller (and CP/M) would not
>even know that it's a 5.25 instead of an 8"; my Cromemcos certainly don't,
>although a different FDC might well require some mods to the BIOS.
Different FDC WILL require a different bios. Same for SERIAL IO.
I think you might have misunderstood, Allison; sounds like you thought I was
talking about replacing an FDC with one other than what the BIOS is configured
for; obviously that will require mods to the BIOS.
What I was responding to was a previous post that suggested replacing an 8"
drive with a 5 1/4" HD drive might require mods to the BIOS, and I just wanted
to mention that this is not the case with a Cromemco 16/64FDC, to which a
TM848 and a JU475 appear identical as long as the jumpers on the 5 1/4 drive
are set correctly and it supplies /READY, and that this may also apply to some
other controllers. Also, if the controller has both 8" and 5 1/4 connectors and
they are effectively in parallel as they are on the Cromemco, you may not
even need a 50<>34 pin adapter cable.
Nevertheless, controllers meant for some of the older, non-'standard' 8" drives
probably will require changes to the BIOS, and likely also hardware mods.
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