linux-mips-fnet
[Top] [All Lists]

Re: m700-10 success

To: linux-mips@fnet.fr
Subject: Re: m700-10 success
From: Systemkennung Linux <linux@mailhost.uni-koblenz.de>
Date: Thu, 9 May 1996 16:18:59 +0200 (MET DST)
In-reply-to: <199605091112.NAA30905@pallas.spacetec.no> from "Tor Arntsen" at May 9, 96 01:12:09 pm
Hi,

> >Don't even think about it!

Why?

> The real reason I'm interested in BE for Linux/MIPS is as I said that Sun
> and SGI use it.  So are you saying that it can't be done for Jazz boxes? 
> That's bad news :-(

Jazz box isn't Jazz box.  The M700 has the endian switching hardware.  I've
recently tried to boot the configuration disk from the Magnum on the M700
but the Oily didn' accept the disk.  I suspect the boot disk was the problem -
opposed to my Acer the M700 does still have the endian switch for the kernel
mode.

> Interesting! I didn't know it could be done in user mode for MIPS, I thought 
> it had to be done no later than during boot (I seem to remember a pin on the 
> chip for this?).  I know PPC can be switched at any time, one task can run BE 
> and the other LE -- at the same time even.  At least that's what I've been 
> told.

You can switch the reverse endian bit on a MIPS at any time but the kernel
byte order is fixed and configured at boot time.  There are some exceptions
to this conncept.  The oldest R2000 CPU don't work properly, the R8000 is
(remember the R8000 is an SGI product, not a real MIPS chip) big endian
only and I think there was also something special with the R6000.  This
as far as memory serves ...

Byteorder switching for the kernel mode requires a motherboard that can
deal with both byteorders.  The trick how to switch the byteorder for the
kernel is that a serial PROM supplies configuration information to the CPU -
among that the byteorder information.  So this PROM has to be changed also.

  Ralf

<Prev in Thread] Current Thread [Next in Thread>