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Re: Deskstation info

To: linux-mips@fnet.fr
Subject: Re: Deskstation info
From: Systemkennung Linux <linux@mailhost.uni-koblenz.de>
Date: Mon, 13 May 1996 11:40:17 +0200 (MET DST)
In-reply-to: <173.199605130803@gladsmuir.algor.co.uk> from "Dom Sweetman" at May 13, 96 09:03:17 am
Hi,

> Bizarre.  It should take 2 cycles/loop on *any* R4600, and 4
> cycles/loop on an R4000/4400.  I'd put money on it *not* taking one
> cycle/loop - only an R10000 can do that!  There are some unlikely
> reasons I can think of for the difference (eg the loop spans a page
> boundary and is in mapped space, when it will repeatedly have to do a
> micro-tlb refill - but I'm sure you're in unmapped space).

Yes, you're right; this effect is bizzare and cannot be explained with some
pagefill effect because it is running in KSEG0.  If this machine wouldn't be
that PC-like I'd say the timers are running at a different clock.  So I'll
check this timer...

> > There are two versions of the R4600; my Tyne had version 1.0 as far as
> > I remember while the SNI box has version 2.0.  The 2.0 chip has some
> > bugfixes; most important is probably the way it accesses primary caches.
> > This bug can be worked around by disabeling interrupts during cacheflush
> > or (untested ...) flushing way B before way A of the cache.
> 
> I don't recall anything on the published Rev 1 buglist which would
> affect this.  Now you've got me intrigued... I'd better go look this up!

I wouldn't wonder if thisone isn't documented.  Write me if you don't find it
in the docs.

   Ralf

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