IBM-PC and SCSI

From: Lawrence Walker <lgwalker_at_look.ca>
Date: Fri Dec 29 16:16:48 2000

> > However I have no info on whether it would be possible to add a SCSI
> > card to an IBM-PC. I have an Adaptec 1522A ISA SCSI card and likely
> > others in my card box. Was there a SCSI card for the PC ? If so,
> > would this possibly, with this configuration, allow you to transcend
> > the 5-slot limits of the PC. And of course to have 1 meg storage for
> > programs. WHEEEEE!!!
>
> I think it's possible, although I have no idea if a commercial card
> was ever produced.
>
> SCSI-1 had an 8 bit databus, and there were a number of SCSI interface
> chips that also used an 8 bit databus on host side -- the most common
> being the well-known NCR 5380. Sticking one of those on an 8 bit ISA
> card is not hard -- in fact I've seen cards like that.
>
> All versions of the PC BIOS after the original one support BIOS
> extension ROMs on peripheral cards. This is needed to boot from any
> device other than a standard floppy drive -- basically the PC
> motherboard BIOS knows how to boot floppy drives and nothing else. If
> you want to boot from a hard disk or something, then the hard disk
> controller needs to have a BIOS extension ROM that (amongst other
> things) contains drivers for that controller.
>
> So in theory it's possible to make an 8 bit SCSI controller with the
> necessary extension ROM to allow the PC to boot from a SCSI drive.
>
> I have never seen one (all the 8 bit SCSI cards I have don't have a
> BIOS extension ROM on them), but that doesn't mean they don't exist.
>
> -tony
>
In thinking about it I forgot about the Intel Onboard 386 card
installed in it. I imagine that takes over all the functions from the
original 8086 Bios so installing any 8bit SCSI should work. Now I'm
wondering about expanding 5150 or any clones capacities using
the SCSI chain.
 Thanks all. I should have thought about it further before firing off
the SOS but this applies to any regular PC-clone 8-bit as well.

ciao larry



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Received on Fri Dec 29 2000 - 16:16:48 GMT