Subject: Re: SCSI network
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Todd Whitesel <>
List: tech-kern
Date: 09/30/1999 23:53:46
> I'm contemplating using SCSI interfaces as a networking medium.  Does

This would be very cool ... potentially faster than 100bt, cheaper than

And for machines that will never have 100bt hardware, it would allow you
to get at them quicker by using another machine as a router.

> anyone have any thoughts on where I should look for (a) convincing a
> machine that it should speak on other than ID 7 or (b) convincing a

Some machines have a eeprom/nvram setting for the host's SCSI ID, but
I expect that this is only used by the boot firmware. You'd probably have
to UTSL to find the relevant kernel code.

> Oh, it is also important that both hosts be able to speak to disks on
> the bus.  (Yes, I do intend to make sure they use disjoint subsets of
> the drives present. :-)

This is definitely possible; it's been done before. Back in the heyday of
the Apple II in elementary schools, you could buy a SCSI card from CMS
peripherals that would let you share one hard drive among multiple hosts
on the same bus. As you'd expect, read-only partitions were accessible to
all hosts and writable partitions were exclusive to one host.

I'm pretty sure they used an NCR 5380 with smarter host software. All
the Apple-branded SCSI hardware from that era did.

Todd Whitesel
toddpw @