Xref: utzoo unix-pc.general:2844 comp.sys.att:6348
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!amdahl!pacbell!pbhacker!tlh
From: tlh@pbhacker.UUCP (Lee Hounshell)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: 3.5" floppy disk revisited on the UNIX pc ...
Keywords: 3.5" floppy, 720K, more space, backups
Message-ID: <115@pbhacker.UUCP>
Date: 4 May 89 14:21:43 GMT
References: <695@icus.islp.ny.us>
Reply-To: tlh@pbhacker.UUCP (PUT YOUR NAME HERE)
Organization: Pacific * Bell, San Ramon, CA
Lines: 16

In article <695@icus.islp.ny.us> lenny@icus.islp.ny.us (Lenny Tropiano) writes:
>Now how did we manage to get both drives on the UNIX pc at once, since the
>hardware only supports one ...  Well it's sorta a hack, but basically it's
>a mechanical switch (SPDT) that switches the FDRIVE0* signal (pin 10) between
>the 5.25" drive (360K) and the 3.5" drive (720K).

Instead of using a mechanical switch, why not change the system's device
drivers to make use of the 4th LED as a switch.  You would still only be able
to access one drive at a time, but you could do it remotely and not have to
manually flip a switch.  Here's how it might be done.. if the 5 1/4 drive
device file is accessed, the disk device driver would turn "off" the fourth
LED and (with some minor main-board modifications) this would cause a physical
connection to be made with the 5 1/4 drive.  If the 3.5 device file is accessed,
the exact opposite would occur.  comments?

Lee Hounshell