From: John Kim (kim_at_stormhaven.org)
Date: Wed Mar 03 1999 - 12:23:14 EST
On Wed, 3 Mar 1999, Mark Bell wrote:
>
> You have to weigh the pros and cons. :) For memory hungry
> applications, the degredation in system performance above
> 64megs due to caching issues might be miniscule compared
> to the headaches users are suffering by using 64megs or
> less of physical ram. The memory WILL be used, but caching
Exactly. Uncached RAM will usually run at about 90%-60% the
speed of cached RAM (depending on your app and processor).
But memory swapped to disk will run at about 0.02% the speed
of cached RAM.
> is absent. BTW, the HX chipset can cache more than 64megs
> because it was targeted towards the server market where
> memory can make all the difference in the world. I still
> keep HX MBs in storage just for clients who use Pentium
> servers or want another one.
I'm not sure I buy that. The HX came out before all the
chipsets limited to 64MB of cached RAM. One line of thought
says that Intel ran into technical problems supporting SDRAM
and a large cache (all the chipsets limited to 64MB can use
SDRAM, the HX has no such limit but cannot use SDRAM). The
other more sinister line of thought says Intel wanted to
protect their Pentium Pro which was a cash cow for the server
market, so they deliberately crippled the later Pentium
chipsets to only support 64MB of RAM cached (the TX came out
when 32MB and 64MB in a system was becoming common).
As a result, if you wanted more than 64MB of cached SDRAM, you
had to buy a (more expensive) Pentium Pro system. If you
tried to save money with a normal Pentium system, you were
either limited to 64MB of cached memory, or you had to give up
the ability to use SDRAM (which as it turns out only gave you
about 1%-5% better speed, but it was new back then so most
people didn't know). I had to agonize over all this when I
bought my desktop system in late '97. Whether it was
intentional or not by Intel, it caused many people a lot of
grief.
-- John H. Kim kim_at_stormhaven.org
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