From: Brandon S. Allbery (bsa@kf8nh.wariat.org)
Date: 06/30/93 

From: bsa@kf8nh.wariat.org (Brandon S. Allbery)
Subject: Re: SUMMARY: Linux performance: WOW! (was: OUCH!)
Date: Wed, 30 Jun 1993 23:01:57 GMT

In article <20smjf$i40@fnnews.fnal.gov> rohrer@fncrd6.fnal.gov (Keith Rohrer) writes:
>In article <1993Jun30.140438.26746@texhrc.uucp>, pyeatt@Texaco.com (Larry D. Pyeatt) writes:
>|> common explaination is "cache tag ram." For some stupid reason,
>|> most motherboards come with enough cache tag ram so that they can
>|> cache the first 16M, but not the second 16M. So, even with the cache
>|> enabled, and 256K of cache installed, it can only cache the lower 16M.
>
>Then why was the big speed jump from limiting the RAM to the lower 16 mbytes?
>16 megabytes WITHOUT cache was faster than 32 megabytes WITH cache!

Probably because Linux in > 16MB will preferentially put the buffers < 16MB
and programs above it, so it can do DMA to/from the buffers. The 16MB magic
number is due to ISA's inability to support DMA beyond 16MB.

++Brandon 

-- 
Brandon S. Allbery         kf8nh@kf8nh.ampr.org          bsa@kf8nh.wariat.org

It's not too late to turn back from the "Gates" of Hell...
Linux: the free 32-bit operating system, available NOW. Why waaaaaait for NT?