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Re: Ping

To: riscy@sunsite.unc.edu
Subject: Re: Ping
From: Daniel.Veillard@imag.fr (Daniel Veillard)
Date: Thu, 16 Dec 93 17:59:13 +0100
Cc: Daniel.Veillard@imag.fr
In-reply-to: Your message of "Thu, 16 Dec 93 10:36:15 EST." <199312161534.AA21628@avignon.daimi.aau.dk>
Tommy Thorn wrote
>Being not much of a HW guy, but wanting to do at least something,
>I've been studing the MMU and exception handling of the r4000 and
>r4200 carefully. I even consider extending the SPIM r2000/r3000
>simulator to cover MIPS III (the ISA of r4x00).

   I had a look in this direction too, but the current implementation
of SPIM doesn't seems to emulate anything concerning the exception
handling of the MIPS familly especially the TLB related exceptions.

> I've also been
>playing with cross development tools.

  I got in touch with some people trying to add GCC support for
64 bit operations and got a version of GAS abble to assemble
64 bit specific stuff. One question concerning the Mips port concern
the extended adressing capabilities of the Mips chips, should we
use it or restain memory adressing to the same of the [34]86,
I suppose too that maintaining compatibility with Little Endian
mode would avoid some weird porting problems.

>I'm a bit worried about porting Linux without some sort of
>coordination with Linus. From what I hear, the (ongoing) m68k
>port hasn't tried to isolate machine dependent parts. Shouldn't
>we/someone contact Linus and the kernel channel (I'm on it)?

stuff I wrote about looking for source from other R4000 OSes deleted
> >   - Is there any other sources available publicly which may
> > help porting Linux ?
> >   - Any comments ?
>Even getting access to a commercial unix for the MIPS is very
>dangeous. Don't even think about it. We would risk a lawsuit.
>Every bit of code in Linux must be *absolutely* free (in the GPL

  I admit looking at commercial sources is dangerous and should be
prohibited for working on this project, but looking at free sources
looking for HW programming tips should be Ok.

>There are other publicly sources which we could study: NetBSD
>is ported to MIPS, I think. Mach is for sure, but double check
>copyright and licence.

  Looking at Mach sources it seems that DecStations, and some AST
machines. But I'm afraid no machine based on ARC design are supported.
What about NetBSD ? 
>I really don't think we would gain much though, as the hard part is
>always getting good HW docs. This should not be a problem with riscy.


>Offering binary compatibility might be doable and possible worthwhile.
>What I would much rather see is the software supplied the ARC 100
>design, if any. I would like to know if we get the CPU from reset,
>or if there is a boot PROM we could/should build on?

  It seems there is a 64 Kb boot EEPROM which in turn launch a
program stored in a 256 Kb Flash EPROM. The Flash EPROM can be filled
using a floppy with the HAL code for booting Windows-NT or specific
code for UNIX bootstrap. But this kind of information should be specified
precisely into the ARC design (I hope so !). 

>I hope I can afford riscy.

  so do I,


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