2 floppy drives on the Unix PC (was: 3.5 inch drives on Unix PC)

[Brad Isley]

In article <2491 at ttardis.UUCP> rlw at ttardis.UUCP (Ron Wilson) writes:
>In article <9221 at stiatl.UUCP>, bgi at stiatl.UUCP (Brad Isley) writes:
>>In article <22605 at pasteur.Berkeley.EDU> sjohn at cory.Berkeley.EDU (John Sasinowski) writes:
>>>	I am interested in adding a 3.5" drive to my Unix PC to make
>>>backing up the hard disk easier.  Jameco Electronics has a drive that
...
>>the sketchy requirements for making a 3.5" floppy work in the 3b1.  If it's
...
[ notes on jumper settings... ]
>
>Sounds good. Now, the next question:
>
>How about 2 floppy drives? (the 5.25 inch already there, plus, the
>3.5 inch added on (externally, of course, but no problem for me))

This I have no experience with except that I know you can plug in and unplug
a floppy drive in a 3b1 all day and not cause any problems if the system isn't
accessing the drive.  This implies that you could get real sloppy and run the
cables outside the case and plug in whatever you want to use at the time.  Or
you could be neat about it and connect both drives.  One method of doing this
would require two things: 1) one drive will be jumpered for drive select 1
instead of 0. 2) the installation of a switch in the cable between the
motherboard and the drives.  This switch would flip-flop the two drive select
lines. Since the 3b1 only knows how to talk to one floppy (ds0 - or so I have
heard!) you just flip the switch to the one you want to use.  Any other similar
switching scheme should work.

>Also, what about the high density 3.5 inch drives? - are these simply
>more tracks? or do they require more sectors per track?

This also can be done.  It requires a modification to the motherboard.  You
must replace a crystal controlling the floppy data rate (again, or so I have
heard!)  I haven't tried this one.  I've just heard that it has been done.
It's more of a one-way street.  Do this and you can't read standard density.

>Thanks in advance.

No probs.
-- 
Brad Isley, yer local tools blacksmith.
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What, me worry ?