PCs that support only one floppy drive in hardware

Tim Mann tim at tim-mann.org
Sat Oct 8 16:25:41 CDT 2005


On Sat, 8 Oct 2005 03:25:49 -0500 (CDT), cctech-request at classiccmp.org wrote:
> Message: 22
> Date: Fri, 7 Oct 2005 21:51:09 -0700
> From: jim stephens <james.w.stephens at gmail.com>
> Subject: Re: TEAC FD-55GFR = Quad Density?
> To: "General Discussion: On-Topic and Off-Topic Posts"
> 	<cctalk at classiccmp.org>
> Message-ID:
> 	<ae0bc2000510072151o541c0ad3u8dbc114f37216beb at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> <snip>
> >
> >
> > <snip>
> > Actually, I am still slowly getting over my long painful struggle to get
> > two floppy drives enabled on a Dell Optiplex system. There's support
> > for a second floppy in the BIOS but it appears the hardware support is
> > entirely missing. I had to just do away with the 3-1/2" disk to get a
> > 5-1/4" disk installed in one of my (many, since I get them for < $5 all
> > kitted out with Pentium III processors) beloved (!!??!!) Optiplex boxes.
> > Was there THAT much savings in not including hardware support for two
> > floppies, DELL? Why not patch settings for the second drive out of the
> > BIOS so we don't pound our heads against the wall trying??
> >
> > I'm curious about the comment about second drive support missing. I
> am curious why the addition of a proper multiheaded cable doesnt
> fix this?
> 
> they actually dont drive the drive select in the cable?

I built a new machine around an EPoX 9NPA nForce 4 motherboard and found
out to my surprise that it was only capable of running one floppy drive.
In my case the BIOS provides no way to enable a second drive, so at
least it's consistent.  Having a BIOS that lets you put in settings for
a second drive when the hardware doesn't support it would really be a
screwup.

EPoX makes schematics available, so I downloaded one and studied it to
try to confirm whether there really was no way to get a second drive to
work.  It turns out the super-IO chip they use to run the floppies and
several other system functions (fan control, temperature sensors, serial
and parallel ports, etc.) has only a limited number of pins.  Several
have multiple functions, and the motherboard designer has to select
which function he wants to use for each pin and do without the others.
EPoX chose to use the pins that could have driven the second floppy's
motor-on and drive select for other functions (I forget what offhand). 
So those pins are no-connects on the floppy cable.

As a small compensation, it's possible to reconfigure the parallel port
as an external floppy connector.  If you do that, you can put two drives
on it.  (Whoopee.)

This all is not a huge deal for me since I can pop a Catweasel card into
the machine if I really want more floppies in it, but it's a bit annoying.

-- 
Tim Mann  tim at tim-mann.org  http://tim-mann.org/



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