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From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: mount vs. 3.5" drives
Message-ID: <2146@cbmvax.UUCP>
Date: Tue, 21-Jul-87 16:31:30 EDT
Article-I.D.: cbmvax.2146
Posted: Tue Jul 21 16:31:30 1987
Date-Received: Thu, 23-Jul-87 05:33:04 EDT
References: <13964@watmath.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 40

in article <13964@watmath.UUCP>, sbmueller@watmath.UUCP (Stephan Mueller) says:
> 
> Please do tell then, why must I still do a mount on my 5.25" official C-A
> drive, to use it under WB1.2?  It is obviously, as you say, recognized
> by the machine (eg. the Transformer knows about it without a mount).

Sounds like maybe a 1.2 feature?  Having no need for the beast myself, I've
never used a 5.25" drive, but I do know the hardware well enough to state
that the system is capable of adding it in without a mount if the software
designers had decided that was a good thing to do.  Perhaps it's left as an
option so that thing like the PC Disk utilities work OK.

> Also, why do I get DF1:BAD, DF2:BAD, DF3:BAD if the 5.25 isn't turned on?

All your disks are daisy-chained together, sharing common data and control
lines.  If you don't supply power to the 5.25" drive, but leave it connected,
those common lines will be affected by the undefined action of the switched
off IC inputs.  This undefined action is usually not a good thing, I've seen
it cause problems in machines long before the Amiga came out.

> What can I do to stop this (besides always turn on the drive).  

Disconnect it.

> What must I do to the animal to have it do automatic diskchanges?  (I've had
> it longer than the warranty, so I ain't worried about breaking nuthin.)

The diskchange signal is usually a function of the drive mechanism.  There's
a microswitch of some kind in the 3.5" drive's pushbutton that results in
the open-collector level /CHNG signal from the drive to be asserted (pulled
low, in this case).  With a little bit of re-engineering of your disk
eject button to trigger a microswitch, and maybe an extra TTL chip or two,
you could probably add this to the 5.25" disk.  The best thing to do would
be to 'scope out exactly what the 3.5" /CHNG signal looks like, and then
build a similar thing on the larger drive.

-- 
Dave Haynie     Commodore-Amiga    Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh
"The A2000 Guy"                    PLINK : D-DAVE H             BIX   : hazy
     "Catch a wave and you're sittin' on top of the world" -Beach Boys