[coreboot] 486 Motherboard from scratch

Guillaume Knispel gknispel at avencall.com
Sat Nov 24 01:07:41 CET 2012

On Sat, 24 Nov 2012 00:06:45 +0100
Peter Stuge <peter at stuge.se> wrote:

> Rex O'Regan wrote:
> > I just chose the 486 as it seems to be about the most basic that
> > can still be used
> Please clarify what you mean by that.

Maybe he had an other thing in mind but I think that you can still run
Linux on a 486, and from what I remember when I programmed on such a
computer it was fairly usable even to compile (simple) programs with
GCC if you were not in a hurry. And you could also use DOS compilers of
that area, which were a lot faster (because of the single target, no
assembly pass, ...)

> > if there are others doing a similar thing with another class
> Noone is.

Either I don't understand the question, or I don't understand the
answer. I'm part of a team that designs a ~ Pentium M class motherboard
for a custom purpose (telephony server / IPBX) using an Intel SoC
(EP80579 -- the CPU in that thing is a Pentium M). (Info here:
design files there : http://git.xivo.fr/?s=xioh under GNU GPLv3+
-- the equipment has the OHANDA trademark that guarantees Open
So it is not just for fun, but it is also not a motherboard for the
next state of the art processor that will only hit the market next year.
And we are a very small team considering the custom blocs in our design
and that we take care of both the hardware and all the BSP.

> Rex O'Regan wrote:
> > Thanks for the input. I have only really done much software before
> > too so this is a big jump for me.
> > 
> > Those numbers
> Certainly for 486 and possibly already for 386 you would look for
> integrated chipsets, rather than using the discrete original Intel
> parts, or you'll most likely need to design custom hardware, e.g. in
> programmable logic, to sit in between.

I agree on that: finding compatible discrete parts risk to be quite
hard, so you should target a System On Chip based board, or try to use
programmable logic but only if you feel very adventurous and have a lot
of time. Don't take my word for it and try to find if you can order
some compatible discrete parts anyway, maybe it is easier than I think.

> Without any hardware experience whatsoever I'd suggest that it takes
> three to five years of full time very fast learning with really good
> mentoring to design a mainboard that can run Doom.

Doom can run poorly on a 386 and starts to be pleasant on a 486.
With today resources, if you make a reasonable initial part choice and
rely on reference designs for all the functional blocs you will
connect, you can probably get to a board of your own of that class and
that does run Doom in probably less than that, depending on the amount
of time you can spend on it day to day.

If it is just a hobby you'll be able to skip some time consuming
and expensive points that are necessary to create a product (like

Still, I agree it would be a time consuming hobby... and you should have
a decent knowledge of electronic engineering or be ready to learn it to
attempt it.

Guillaume Knispel

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