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Re: CVS linux

To: Ralf Baechle <>
Subject: Re: CVS linux
From: "Maciej W. Rozycki" <>
Date: Thu, 3 Apr 2003 16:48:21 +0200 (MET DST)
In-reply-to: <>
Organization: Technical University of Gdansk
Original-recipient: rfc822;
On Thu, 3 Apr 2003, Ralf Baechle wrote:

> I know of one machine where changing the size of the cacheline is supposed
> not to work, that's the MIPS Magnum 4000 and it's close relatives.

 Hmm, why -- is such a change observable externally in any way?  Of
course you can't switch the other way if the s-cache uses a line width of
16 bytes.  Maybe that's the case with the Magnum?

> Anyway, I put the check there for the unlikely case there are broken
> systems out there.  In practice I assume vendors were aware of this
> problem and the check is purely theoretical and for paranoid correctness's
> sake.

 Still V3.0 should be taken into account.

> It seems like changing the configuration to larger cache lines where
> possible should improve performance somewhat.  If all the cache code is

 Why?  It isn't that obvious especially as a p-cache miss costs a single
cycle only.

> working truly correct we also should no longer see VCE exceptions on
> R4000SC processors - the reason why Indys are still a valuable test tool.

 As are DECstations which use the opposite endianness -- so you can test
code both ways.

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail:, PGP key available        +

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