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Re: Can XMOS do occam?

Larry Dickson <tjoccam@xxxxxxxxxxx> writes:

> (1) Is there an occam compiler for the XMOS XS1?

Not yet. We've heard there are plenty of people who'd be interested in
one, but none of us at Kent have the time to do it at the moment -- if
we could sort out some way of funding it it'd be more practical
(e.g. one of the EPSRC commercial development grants). It'd be trivial
to get the Transterpreter (our portable ETC virtual machine) running on
the XS1 architecture, of course, but the performance wouldn't match XC.

If you're curious, there are two ways we could get occam running
natively on the XS1. The easier approach would be to use the existing
compiler, and glue Carl's ETC-to-LLVM translator to XMOS's LLVM-to-XS1
backend, translating the ETC communication instructions into the XS1
equivalents directly. The harder approach would be to add an LLVM
backend to Tock, our new occam compiler, which has been on the to-do
list for a while, but would be a better option in terms of future

> Is the limitation on thread count real, or is it an artifact of some
> software behavior?

It's a hardware limitation. There's no software scheduler yet (it's
harder than it sounds, since one of the advantages of the pool of
hardware threads is the low-latency response to events), so you're
limited to 32 processes on an XS1-G4.

(No idea about placement across multiple chips; it didn't when I last
used the tools but they were working on it.)

> (4) A further point: I have been studying the RepRap 3D printer, and
> have come to its Sanguino3G serial protocol definition, which has a
> master controller (an Atmel-based Sanguino) driving several slave
> controllers - and using polling!

We ported the Transterpreter to various Arduino boards including the
Sanguino last summer, and a replacement for the RepRap firmware in occam
is something that Matt Jadud was considering as a student project. It
doesn't need XS1-grade computing power; the AVR is more than

The existing RepRap firmware really is complete junk! The RepRap design
generally is pretty awful... there are much better 3D printer kits out
there if you're after one.

Here's a presentation I gave in January about occam on the Arduino and
other AVR boards, with pictures of Matt's RepRap:


Adam Sampson                                         <http://offog.org/>