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've also been
playing with cross development tools.
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)?
Now for an old mail:
Daniel Veillard writes:
> from all I've read concerning the riscWS/EISA chipset we
> plan to use, and information I got from the net, it seems that
> the future board will be very similar to the Magnum 4000 machine:
> This kind of compatibility may be interesting for a fast
> port of Linux if we were able to get access to the source of other
> operating system for the Magnum (may help for Device drivers
> and interface with CPU/MMU). I have also heard that Plan 9
> distributed operating system have been ported to the Magnum R4000
> and that free source licence is available for Universities.
> Getting sources of other OS running on Misp Magnum 4000 may help
> developping Linux and that's something we can do before the board
> is available.
> Furthermore, staying compatible with the Magnum products may be
> a good way to offer binary compatibility and run commercial products
> on Linux.
> - Am I completely wrong ?
> - 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
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.
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?
I hope I can afford riscy.