> SCSI on the motherboard:
> For those wanting SCSI, the motherboard wins hands down.
I definitely agree. And the proliferation of CD-ROM is
going to make SCSI more desirable through the next 3-5 years.
The part could be socketed, though PLCC sockets drive me up
the wall around here with unreliable connections.
There are a number of SCSI controller chips worth looking
at, including the NCR 5380 and derivatives (including the
NatSemi DP8490) and the Western Digital 33c93 and derivatives.
I would tend towards the 5380 type, as they are multiple sourced
(cheap), well-known (Seagate ST-01), and can provide reasonable
I wrote the Linux Seagate ST-01 (ie, with the Nat. Semi part) driver, and
I would avoid this part like the plague. The designer obviously failed his
introductory digital circuits class where they taught FSM design, because
the chip can't tell you when the SCSI REQ line transitioned low->high,
only when it's currently high. Faster SCSI devices work OK if you
just sit in a tight loop and blindly write to the port, with slower
SCSI devices, you have to loop, wait for it to go low then high, and
be sure to timeout because you'll miss it a lot. The chip can only
generate an interrupt when the SCSI SEL line is raised, so most of the
time you sit arround spinning your wheels in a loop (and you can't
DMA to it because you need to make sure the status registers have the
IMHO, the 53cf90 series is the best choice I've seen so far, I don't
know about the Western Digital chip, but it rings a bell as the chip
used in the WD7000 controller.