[Oberon] RISC platform issue

nyaaa at nyaaa.de nyaaa at nyaaa.de
Mon Jun 23 13:48:59 CEST 2014

Since Digilent's SPARTAN-3 board has reached its end of life and many
newer development boards only come with SDRAM, I welcome the effort to
add support for it. It would be nice, if cheap boards like Olimex's
MOD-VGA-32M [1] could be used to run Oberon. Not being familiar with
hardware description languages, I am unable to guess what makes
supporting another RAM type than found on the Digilent board so much
more difficult.

Naive as I am, I would believe that you did not have to look any further
than to Papilio DUO, whose production can currently be funded. [2] The
$149 (plus shipping) deluxe bundle comes with 2 MB SRAM and a retro
computing shield, is advertised as open source hardware and might be
worth an investigation. According to the SRAM data sheet, to which the
campaign page links (but which seems to refer to the non-deluxe versions
512K module), it is a 512K x 8 type RAM though, while the Digilent
board's SRAM seems to comprise two 256K x 16 type RAM chips, which from
my very limited understanding means, that the Digilent board allows
32-bit wide memory accesses per cycle while the the Papilio DUO board is
limited to 8-bit wide accesses. I don't know how much that would
complicate a port to that board.

The cleanest solution for a successor to the Digilent board would
probably be a custom design. Again, not being able to make an educated
guess about how difficult such an endeavour would actually be, I imagine
that Papilio DUO could be a starting point for a custom design.
Improvements could be an SD card connector, a LiPo battery connector,
possibly a larger FPGA and wider SRAM. SRAM modules seem to be
significantly more expensive than SDRAM modules though, and for that
reason I still believe that the effort to add support for the latter
would not be wasted. The Atmel MCU on the Papilio DUO could also be
replaced with a more powerful chip, perhaps a PIC32 or a Propeller.

Speaking of which, Parallax is currently in the process of designing a
successor to the Propeller. There seem to be plans to make a Verilog
implementation of the Propeller 1 chip available at some point. A custom
FPGA board for the purpose of developing and testing future Propeller
chips has been announced. [3]

Since Olimex has designed its Duinomite boards as an improved version of
the Maximite in the past, they might be interested in producing an
improved version of the Papilio DUO, if that would not mean much work
for them. A recent blog post of theirs [4] is an interesting read about
their perspective on the Duinomite story. Lest Oberon joins BASIC on its
way into oblivion, interested developers should speak up. Olimex might
be surprised to learn that Oberon is not as dead as they thought at the
end of some older post of theirs [5] and that it has even been ported to
an FPGA board.


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