Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!vsi1!wyse!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: Workstations for Lisp
Message-ID: <21641@winchester.mips.COM>
Date: 14 Jun 89 07:38:58 GMT
References: <486@unipas.fmi.uni-passau.de> <5187@pt.cs.cmu.edu> <EYYf=ky00jcqNYcW4L@cs.cmu.edu> <109577@sun.Eng.Sun.COM> <21525@winchester.mips.COM> <109849@sun.Eng.Sun.COM>
Reply-To: mash@mips.COM (John Mashey)
Organization: MIPS Computer Systems, Inc.
Lines: 29

In article <109849@sun.Eng.Sun.COM> khb@sun.UUCP (Keith Bierman - SPD Languages Marketing -- MTS) writes:
>In article <21525@winchester.mips.COM> mash@mips.COM (John Mashey) writes:
>>Most R2000 or R3000 systems, DS3100 included, use 4-deep write-buffers,
>>often built with R2020 Write Buffers.

>I stand corrected. Now all I have to do is understand why our 3100
>performance does not scale trivially to our M2000 .... suggestions ?
>Memory system had seemed so attractive as an explaination ....
The memory systems are very different.  R2000-based machines use the
simplest-possible cache, i.e., write-thru with 1-word refills on miss.
and cache-word invalidates on partial-word writes.
R3000s are much more complicated, as they can do anywhere from 1 to 32
words/block burst refill, instruction streaming, direct drive of the 
cache rams, optional read-modify-write instead of invalidate for
partial-word writes; they typically have memory systems with more
interleaving, page-mode DRAMs, etc, etc.

>Reverse engineering (i.e. looking at the performance on the same
>codes) one can see the SS1 stalling much more often than stingray.
>Clearly my memory is faulty (or I would not have misquoted the
>MIPS/DEC lit :>).. but my recollection is that 4/330 has a double word
>of buffering.
Oops, I recall seeing that also, but I think I was thinking it was
1 doubleword, rather than 2 32-bit words. Now, I don't know which.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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