4 floppy disk drives on a PC?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jan 16 17:32:43 2005

>
>
> I know we've discussed this before but the right Google search terms are
> eluding me.
>
> Is it possible to get 4 floppy drives onto a PC? If so, how? If I stick

If 'PC' means an IBM5150, then yes, trivially. A: and B: connect to the
intenral drive cable, C: and D: connect to the DC37 socket on the back of
the card. But I guess that's not what you mean (this card supports 360K
and 720K drives only, BTW).

> two controllers in the PC and configure one with a different base address
> and interrupt (assuming I can find a card that allows me to do this) will

The intrrupt is not the problem (you can share interrups on the iSA bus
provided you don't want them both enabled at the same time, which you
wouldn't here). Most controllers, alas, do not support alternative
addresses, but one time, in a fit of madness, I did a cut-and-jumper mod
to add an inverter to one of the address lines going to a UMC disk
controller chip to get it to a different address (this was to put _6_
drives on my PC/XT, the last 2 being 8" on this hacked controller).

> DOS automatically recognize the second controller and extend the drive
> letters C: and D: to the drives on that card?

MS-DOS, and pesumably Windows, will not support 2 disk controllers
automatically , or even easily. I believe linux does, it'll even support
up to 4 drives per controller (if you look at how the drive select bits
are allocated to the output port, it's obvious how this would be extended
for 4 drives). I wrote my on MS-DOS software to handle the 8" drives (I
wanted them to read/write PERQ interchange disks, so only being able to
use them from that special program was not a problem).

-tony
Received on Sun Jan 16 2005 - 17:32:43 GMT