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Sun, 9 Nov 1997 17:25:55 -0500 (EST)
From: "John S. Dyson" <toor@dyson.iquest.net>
Message-Id: <199711092225.RAA27206@dyson.iquest.net>
Subject: Re: Best processor?
In-Reply-To: <Pine.BSF.3.96.971109160728.27308A-100000@picnic.mat.net> from Chuck Robey at "Nov 9, 97 04:10:10 pm"
To: chuckr@Glue.umd.edu (Chuck Robey)
Date: Sun, 9 Nov 1997 17:25:54 -0500 (EST)
Cc: toor@dyson.iquest.net, nate@mt.sri.com, perlsta@cs.sunyit.edu,
gpalmer@freebsd.org, freebsd-smp@freebsd.org
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Chuck Robey said:
> On Sun, 9 Nov 1997, John S. Dyson wrote:
>
> > If you are talking about 233MHz PII processors vs. 200MHz PPro processors, it
> > is harder to decide on which processor is faster, but I do think that the PII
> > will win out on average. Clock your PPro at 233MHz, and the PPro will win out,
> > except for MMX type apps, or on memory intensive apps, where the LX chipset and
> > SDRAM memory speeds help.
>
> I can't remember where I read it (because I read a protected mode list
> also, and game producers comment on this a lot) but I'd read where the MMX
> instructions are not proving to be any real help there.
>
Well, with MMX you do have to seriously recode your apps. The biggest problem
with MMX that I see, is that it doesn't appear to be of much help with 32Bit
DSP ops. When working in 16Bit land for certain apps, one has to be much
more careful. We (FreeBSD) don't support MMX yet, other than it will probably
work if you want to try it.
>
> Exactly how much L1 cache is on the PPro 512K L2 chips vs. the PII 512K L2
> chips, do you know?
>
The PII has 16K+16K as opposed to PPro 8K+8K. I seem to remember that the
associativity might be better on the PII also. Since that is less in the
area of diminishing returns (unlike the upgrade from 256K to 512K in a
single cpu system, which mostly helps just a little), I would expect that
the larger L1 makes a substantial difference, especially since the PII has
slower L2 access, and the cost of a miss is higher. Note that the PPro has only
2 pages of L1 data cache, while the PII has 4 pages. That has to help the
multi user system performance when all new pages have to be zeroed, since
one is a little less likely to fully erase the valuable cache. (Just a
guess.)
The 16K+16K must really help when the benchmark doesn't fit in the 8K+8K
though :-).
--
John
dyson@freebsd.org
jdyson@nc.com