Re: Two computers on single SCSI chain

[dempson@swell.actrix.gen.nz (David Empson)]

In article <93Aug1.110210-0600.138440@amisk.cs.ualberta.ca> glyn@cs.ualberta.ca writes:
> Has anyone tried using two computers on a single SCSI chain?
> In particular, I'm wondering if given a SCSI controller in both
> my IIgs and IBM 286, whether they would be able to share a SCSI
> tape backup (or other peripherals) without having to dis- and
> re-connect the tape unit each time.  --  I'm trying to figure out
> which peripherals to buy for a minimum of cost.

In theory, this can be done.  Both SCSI controllers must be set to a
different ID, and you can't have both of them accessing a device at
the same time!

In practice, you might run into problems.  For example, both SCSI
controllers must correctly implement the SCSI arbitration sequence.
I'm pretty sure that the original Apple SCSI card doesn't do this, so
it can't be used with another controller on the bus.
The Mac Plus may have similar limitations (but I expect the Mac SE and
later should be OK).
PC SCSI cards are a bit of a grey area - some of them are so simple
that they may have skimped on parts of the standard.

I think the High-speed SCSI card is OK, but I don't know about the
RamFAST.  It claims that it doesn't use a SCSI ID, and I don't
understand how it can do this.

I have not tried connecting two hosts to the same SCSI bus, but I have
heard of people who have done this (with an Apple II and Macintosh).
-- 
David Empson                                                               
dempson@swell.actrix.gen.nz                                                
Snail mail: P.O. Box 27-103, Wellington, New Zealand