Need buying advice for 386 and Unix

[Thomas Hoberg]

In article <49991 at bigtex.cactus.org>, james at bigtex.cactus.org (James Van Artsdalen) writes:
|> In <5682 at crash.cts.com>, jca at pnet01.cts.com (John C. Archambeau) wrote:
|> 
|> > A 486/33 motherboard will yield about 14 to 15 MIPS.  But keep in
|> > mind the bottleneck going across the ISA bus.  A 64-bit processor
|> > running on a 16-bit bus.
|> 
|> There's nothing 64-bit about a 486.  It does have 128-bit cache lines.
|> 
|> > Sort of reminds me of a traffic jam when a highway suddenly goes
|> > from 4 lanes to 1 (which is the correct ratio).  Do NOT get a 486
|> > unless you're going to go EISA or MCA.  It's a waste of CPU bus
|> > bandwidth if you don't.
|> 
|> I disagree here.  The data coming off of the hard disk is much less
|> than the bandwidth of the AT bus.  Therefore you can't win with just
|> an EISA hard disk controller.  What you CAN win with is a caching
|> controller, or a controller that can do DMA & has a unix driver that
|> can use it, or some other optimization not related to the bus
|> bandwidth.  Caching helps ISA too.
If EISA and ISA were to cost the same or perhaps 10-20% difference, I'd 
certainly recommend EISA, even though right now, there very little to be gained
by it in terms of performance. I agree that the current bandwidth provided by
the ISA bus is sufficient for disks and frame buffers. The combination of an
Adaptec 154x bus mastering SCSI controller and about five 3 1/2" 200MB SCSI
drives and a disk striping driver for ISC's HPDD should be difficult to beat
(not match) for any EISA board right now. I got a Chips and Technologies
based Taiwan i486 clone for about a third of the price I'd have to pay for any
EISA board right now. Sure, it doesnt support burst mode DRAM accesses and
second stage caches, but I tend to think that those bells and whistles hurt
the bang-to-the-buck ratio more than the're really worth. If what everybody
keeps telling us is true, Multi Media is comming fast. That's when the EISA
bus will become a must: With FDDI networks carrying real-time compressed
HDTV video data, the ISA bus will become obsolete. That is probably still one
or two years away yet. By then you will probably junk your present system 
anyway--computers are like kleenex:before you had them, you wouldn't have 
thought you'd need them and you wouldn't want to keep the same one around for
any extendet period of time...
----
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