[Oberon] RISC / Can ETHO be ported to ARM?

Paul Reed paulreed at paddedcell.com
Fri Nov 2 14:29:15 CET 2012

> From: Peter Matthias <PeterMatthias at web.de>
> Subject: Re: [Oberon] Can ETHO be ported to ARM?

Hi Peter,

> Interesting interview. I hope the new books will be out soon. His RISC
> processor will be only for education purposes with 1MB RAM...

Prof. Wirth's RISC processor has a full 32-bit address space.  It's just
that the Xilinx/Digilent Spartan-3 Starter FPGA board we are using happens
to have 1MB RAM.

BTW anyone who thinks that 1MB is not a lot of memory probably doesn't
belong on this list ;-)  Also you might upset many embedded programmers,
who still *dream* of having 1MB RAM! :)

> Personally I would like to see an Oberon like system on the Raspberry Pi.
> I
> will check for a compiler. However, if I do it, it would be a fun project

It's fun until you try to implement USB, which is necessary for the
keyboard and mouse (I have GPIO and framebuffer working nicely in Oberon,
didn't take too long).

The Broadcom GPU+ARM system-on-chip has a USB IP block licensed from
Synopsys which is a highly-configurable (aka incredibly complicated) USB
2.0 On-The-Go host-and-device-capable design, with several functions
disabled or hardwired by the Raspberry Pi Foundation.

Cambridge University/Alex Chadwick's "Baking Pi" tiny bare metal ARM
assembler tutorial programs, are linked with his library of nearly 7000
lines of C code, if they need to access USB.  And because USB interrupt
transfers are not yet supported (only control transfers), only about 6 out
of the 12 keyboards he's tried work so far...

This is not a problem with the Raspberry Pi, per se: all USB libraries are
huge and complicated.  The Pi actually looks pretty simple compared with a
BeagleBoard or a Freescale i.MX (simpler ARM boards don't tend to have
framebuffer video), and you can't argue with the price.  :)


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