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Re: XZ graphics specs...

To: "William J. Earl" <wje@cthulhu.engr.sgi.com>
Subject: Re: XZ graphics specs...
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Sat, 15 Jan 2000 12:47:26 +0100
Cc: "Soren S. Jorvang" <soren@wheel.dk>, John Michael Clemens <clemej@rpi.edu>, linux@cthulhu.engr.sgi.com
In-reply-to: <14464.1378.215834.722831@liveoak.engr.sgi.com>
References: <14462.24718.670816.841437@liveoak.engr.sgi.com> <Pine.A41.3.96.1000113224501.118018F-100000@vcmr-19.rcs.rpi.edu> <20000114055613.A26954@gnyf.wheel.dk> <20000114114430.A4278@uni-koblenz.de> <14464.1378.215834.722831@liveoak.engr.sgi.com>
Sender: owner-linuxmips@oss.sgi.com
On Fri, Jan 14, 2000 at 09:28:02PM -0800, William J. Earl wrote:

>  > In theory yes.  In practice all firmware that I've seen so far seems to
>  > be rather fragile and for some systems also very performance limited as
>  > it's running from uncached memory (veeeerry slooow) or at times even
>  > from 8-bit wide PROMs which is so slow that it blows every meassure for
>  > slowness.  Not to mention other problems.  So this should really be
>  > considered a better than nothing solution.
>  > 
>  > That being said, Ulf Carlsson has implemented a PROM console which is
>  > in the CVS archive.  Try it, I'm interested in reports.
> 
>       On some platforms the PROM code is actually copied to main memory
> and executed (cached) from there.  If I remember correctly, O2 works that
> way.  Indy is probably in the slow (possibly very slow) category.

Running from a PROM would explain why the Indy firmware crashes with
enabled L2 caches - the circuitry just wasn't designed to deal with the
type of access cycles (bursts?) as used by the l2 cache controller.
No major problem in practice.

  Ralf

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