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Re: Debian ports for RiscPC, ARM710, etc.

On Mon, Sep 28, 1998 at 02:57:47PM -0700, Jim Pick wrote:
> I think I may be confused about what constitutes a "RiscPC".
> I thought they all had StrongARM CPUs, but I think I was wrong.
> Acorn's web site isn't much help.
> I see there is the Acorn RiscPC 600 series, Acorn RiscPC 700 series,
> and then the Acorn StrongARM RiscPC.  I am guessing that the 600 and
> 700 series are using chips that only support the armv3 instruction
> set?  If that's the case, then those are RiscPCs, but they can't
> handle halfword instructions.  But the StrongARM RiscPC can handle the
> halfword instructions, right?

Okay, Acorn have produced a number of models over their lifetime.
For the pedants on this list, I only cover the ARM based models which
were actually mass-produced.  I don't see a port of ARMLinux to the sole
remaining M4 in existance happening any time soon.

Prior to the RiscPC, all models have ARM2 or ARM3 processors (armv2)
which still have some devoted users (including myself) but said users
will be competent enough to handle their own installations.  There's no
ELF solution available for these machines right now.

RiscPCs were originally shipped with ARM610, then with ARM710 (both
armv3).  The RiscPC bus was not designed to handle some of the features of
StrongARM (since it wasn't known about at design time), so the card which
the SA sits on has to emulate some of the features of the earlier CPUs.
As a result, half-word (and possibly load signed byte?) instructions
do not work.

Acorn also produced the A7000 and the A7000+, based on the ARM7500 and
7500FE respectively.  ARMLinux does not currently handle the console of
these machines due to a lack of VRAM.  These processors are ARM7-cores
(ie armv3) with integrated video, io and other gunk.  The only interesting
thing is that the 7500FE has built in floating point.

So a -fsoft-float solution is definitely best for all current models.

> I was getting confused when people said that RiscPCs couldn't handle
> the halfword instructions, because I initially thought that all RiscPC
> models were using the StrongARM.
> If that's the case, then we have a pretty clean split between armv3
> machines, and StrongARM machines (NetWinder, EBSA, and StrongARM
> RiscPC).  Then the current Debian "arm" distribution should be work on
> any StrongARM based machine, including the StrongARM RiscPC.  The
> RiscPC 600, 700 and some older models will need to use the "armv3"
> distribution.
> Or do I still have it wrong?

Sorry, it's not nearly that simple.  Can we have a debian-arm and a
debian-acorn distribution, otherwise people will be confused.  People
would have been more confused had Phoebe ever made it into production.
(This would be an Acorn machine which supported the StrongARM properly)

Matthew Wilcox <willy@bofh.ai>
"I decry the current tendency to seek patents on algorithms.  There are
better ways to earn a living than to prevent other people from making use of
one's contributions to computer science."  -- Donald E. Knuth, TAoCP vol 3

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