On Tue, 6 Jun 2000 willy@thepuffingroup.com wrote:
> On Tue, Jun 06, 2000 at 03:32:18PM +0200, scoetzee@voltex.co.za wrote:
> > this is fine, as you can always add more controllers, but theoretically (never
> > tried myself)
> > you can attach 32 SCSI 3 devices to a scsi3 bus.
>
> but i've never understood _why_. if you read the docs from, say, SGI,
> they recommend not putting more than 4 drives on a chain as they will have
> completely saturated the bandwidth. if your devices aren't high-enough
> bandwidth to saturate the bus, then why not put them on a cheaper bus
> with more controllers (like, er, IDE).
You do get some other devices which can be put on a SCSI bus but not often
IDE - scanners, for example. Now, of course, you can also get USB
versions...
The ability to have many devices per bus generally collapses: if they are
slow devices, use USB. If they are fast devices, having more than a few
per controller will strangle throughput anyway, so you end up with,
perhaps... up to four drives per controller, like IDE!
> ok, you might argue that you only have N slots in your machine --
> there are some pretty nice quad-tulip cards available, i don't see why
> people shouldn't make quad-IDE controllers (2 busses per controller =>
> 16 devices.)
I think I've seen a couple around; my current motherboard has four IDE
channels on, too.
James.
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