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Date: Wed, 9 Apr 1997 15:43:48 -0500 (CDT)
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From: Tony Kimball <Anthony.Kimball@East.Sun.COM>
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To: dave@persprog.com
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Subject: Re: Pentuim or Pentuim Pro ?
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Quoth Dave Alderman on Wed, 9 April:
: 
: Let's not forget that SDRAM may show better performance with the
: upcoming faster processors as well, although if I know this industry,
: the existing SDRAM will be inadequate in some way or another.

It's tied to the bus speed.  66 MHz SDRAM will not reliably deliver a
read per clock on an 83 or 100 MHz bus.  You can buy 100 MHz SDRAM and
put it on a 66 MHz bus and move it to a faster board in the future,
but it is a violation of the JIT purchasing methodology (the large 100
MHz cost premium will drop in the future), and may not make sense if
you resell the old board anyhow.

: That 64Meg limitation can be a real killer for loaded machines and even
: for certain mathematical tasks like simulation or modeling.  Intel
: really wants you to buy the Pentium Pro or Pentium II and this is one of
: their "incentives".
: 
: What is "substantially better"?  A ballpark figure would be fine.

That's the best I can give, since I've never compared systems with
similar processor/bus/chipset differing only in RAM architecture.  I'm
guessing 12-15% win (66MHz SDRAM vs. 60ns EDO, which is approximate
cost parity) for my application, a direct ODE solver which is
essentially (in terms of architectural performance model) a large
number of iterations of a very poorly written 24MB bcopy.  Probably
not a very *typical* (meaning "REAL WORLD"?) application.

I could *strongly* benefit from PPro (primarily because of
superscalarization), but today's cost-benefit trade-off favors the
smaller incremental benefit of K6-166/SDRAM.  If my application were
not embarassingly parallel, this would no longer be the case -- for
example, when I convert to an indirect solver.  (Actually, the real
price-performance win in the near future is Alpha.  When the AlphaPC
boards plateau -- in a month or two, perhaps? -- I'm going to have to
seriously consider switching to, ugh, Linux.)