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Re: Question for David Miller or anyone else about R6000 code

To: "Kevin D. Kissell" <kevink@mips.com>
Subject: Re: Question for David Miller or anyone else about R6000 code
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Mon, 6 Dec 1999 09:28:30 -0200
Cc: Linux SGI <linux@cthulhu.engr.sgi.com>
In-reply-to: <004c01bf3fd0$68336790$0ceca8c0@satanas.mips.com>
References: <004c01bf3fd0$68336790$0ceca8c0@satanas.mips.com>
Sender: owner-linuxmips@oss.sgi.com
On Mon, Dec 06, 1999 at 10:58:10AM +0100, Kevin D. Kissell wrote:

> I'm working on cleaning up and enhancing the
> MIPS/Linux code to support the new families
> of CPUs coming out of MIPS Technologies Inc.
> In doing so, I've come across and fixed a number
> of bugs, most of which I've also passed back to
> Ralf Baechle for integration with the moving
> target at linux.sgi.com.   But I came across 
> something this morning that, while not a problem
> for us, puzzles me.   In arch/mips/mm/r6000.c,
> which has your name on it, there is a compiler
> directive to use MIPS III instructions, and the
> resulting code does indeed end up containing
> 64-bit (daddiu, etc.) instructions.   I've never
> actually programmed an R6000, but all of the
> information I have on that processor indicates
> that it is a MIPS II, 32-bit design, and that those
> instructions should therefore cause exceptions.
> 
> Am I mistaken, or is that directive a bug?

It obviously is.  The R6000 code isn't supposed to work and given that
currently none of the Linux/MIPS hackers has a) R6000 documentation and
b) an R6000 machine an R6000 port ever happening is highly unprobable.
As the result of this I think I'm going to just burry the R6000 support
and while I'm at it also the R8000.

  Ralf

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