Cache memory

[Paul De Bra]

Well, let me clear one thing about cache memory: whatever Unix you are
running, you do *not* want to disable cache if at all possible. I don't
know about the Intel cache controller, but I can give you a few numbers
about the Everex Step 386/25 with and without cache. I am running AT&T
Unix System V rel 3.2 and have only one small problem with the cache: I
have to boot my machine at low speed. Once booted there is no more problem
with 25Mhz and the Everex AMMA cache. Here are a few results (you can more
or less guess what the tests do), comparing the 386/25 with and without
cache with a 16 Mhz 6386 and a Sun 386i/250 (the 25Mhz with cache):

TEST			Everex-cache	Everex-nocache	6386	Sun-386i
---------------------------------------------------------------------------
pipes			 6.7		13.7		14.3	13.8
system calls		16.0		33.4		32.5	16.8
function calls		 4.4		10.9		10.5	 5.7
sieve			 3.0		 6.6		 6.5	 3.6
sine			 5.1		 6.5		 8.6	 3.1*
loop			 5.3		10.4		11.2	 9.9
shell script		 1.7		 2.7		 2.9	 2.5
15xsame script &	17.2		29.9		31.3	35.4

(* uses weitek instead of 387 as the others do)

Disabling the cache on this amazingly fast machine degrades it to the level
of a middle of the road 16 Mhz box. So you better make *sure* your high-speed
machine runs your Unix with cache enabled before you buy...

Paul.

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