On 23.05.01, 00:57:12, Andy Ball wrote:
> 
> Hello!
> 
> I seem to be having a lot of SCSI conversations with people
> lately. Mike, my brother-in-law, is probably going to have a
> CD-RW drive as his first SCSI peripheral, but I've sold him
> sufficiently on the joys of SCSI that he may eventually have
> a SCSI hard disk too (and perhaps a DVD-RAM, who knows! :-)
> 
> Plextor's current SCSI CD-RW drives seem to be Ultra SCSI
> (8-bit, 20MHz, possibly single-ended).  I don't know if they
> plan to move to Ultra160 anytime soon.

Between Ultra and U160 there's still Ultra-Wide and Ultra-2-Wide
(LVD). I don't think that differential modes are commonly used on
narrow busses.

> 
> Assuming he goes with Ultra SCSI, I'm thinking of either an
> Adaptec AHA-2930CU (or similar, not sure if that one's
> supported) or something based on a 53c860.  His system
> doesn't have NCR/Symbios BIOS extensions though, so he'll
> need a card with on-board firmware if he's to eventually
> boot from a SCSI drive.
> 
> Since Mike plans to run NetBSD/i386, (something else I sold
> him on ;-) I would welcome suggestions as to what (Ultra)
> SCSI host adaptors are known to work well with that.

If he's to use SCSI disks eventually, he should definitely get at
least an ultra wide host adaptor (almost all of those have a narrow
connector, too, for CD-ROM, CD-RW and the like, or one can use an
adaptor).

There are virtually no more Ultra (narrow) disks any more, and even
single-ended Ultra-wide drives are vanishing fast. But LVD-Disks are
downwards-compatible (i. e. can run in degraded mode at Ultra-Speeds)
with ultra-mode. One problem is that most LVD drives cannot terminate
the bus, and you need an extra terminator, and of course you cannot
terminate a wide bus with a narrow device.


I recommend an NCR/Symbios based host adaptor. Those are usually a lot
cheaper than Adaptec, but at least as good.

Most of those have their own firmware and can boot from disks and
CD-ROM.

I have a Tekram DC-390F (Ultra Wide, 16Bit, 20 MHz), based on Symbios
53C875, and now there are 2 disks, CD-R and DVD-ROM on the narrow
connector, and one disk on the wide connector. With this setup I
cannot use the external connector, that would make an illegal
"Y"-topolgy in the bus.

The DC-390F is dicontinued but you might still pick one up cheap.

The successors DC-315 and DC-395 are based on a different chip
("Tekram S1040"), and I don't know about NetBSD support.

Then there are the more expensive models of the DC-390 series (based
on the well-supported Symbios 53c895): DC-390 U2W (LVD, wide and
narrow connectors), U2B (only wide connectors).

> 
> Since I'm an old fart, I'll probably stick with Fast SCSI-2
> (8-bit, 10MHz, single-ended) myself.  If I build another PC
> for use with NetBSD, I may use a 53c810 PCI host adaptor.
> 
> - Andy.
> 

-- 
Bernd Sieker

NetBSD: The free OS with a money back guarantee!
		-- Tim Rightnour