4 floppy disk drives on a PC?

[Tony Duell]

> 
> 
> 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