Re: gEDA-user: random project idea

[Larry Doolittle <ldoolitt@xxxxxxxxxxxxxxx>]

On Thu, Mar 27, 2008 at 09:28:23PM -0500, John Griessen wrote:
> Larry Doolittle wrote:
>  > Self-reconfigurable FPGAs have been promised for years, but aren't
>  > ready, and probably never will be.
> I guess that's because the fpga makers seem to not want to let out their
> programming details -- probably because they let Mentor and Synplicity
> and the like do all their tools and THEY don't want it let out.

Tools are certainly part of the story.  But it also strikes me as
a chicken-and-egg problem.  The user's don't demand or exercise the
tools because of the conceptual problems and the silicon limitations.

On Thu, Mar 27, 2008 at 08:59:47PM -0400, DJ Delorie wrote:
> What about the new flash-based FPGAs?  Maybe not as big, but they seem
> to be "instant-on".  I suppose we could have a CPLD sequence the
> boot/reset/run sequence.

Where the boot information is kept isn't as important as how to
reprogram it without risk of bricking the board.

> If we can fit it into 6/6 trace/space with 12 mil via holes, that's
> within spec for common prototype fabs (pcb-pool, specifically, which
> does 4 and 6 layer).

6/6 is doable if you slightly cheat the size of the solder pads.

> Now, if I could solder [a spartan-3 FB676] on my hotplate... :-)

I have seen instructions for home-soldering BGAs.  I haven't tried
them myself, and I don't know what the size limits are.

On Thu, Mar 27, 2008 at 09:34:27PM -0500, John Griessen wrote:
>> If anyone wants to talk shop
>> about CPUs in FPGA, like how to add Cache, MMU, and SDRAM to a 32-bit
>> Gray-esque processor, let's find a better list.
>
> I'm not sure about as far as a MMU linux running processor in FPGA,
> I think of buying that in hardware,
> but how hard is it to take a ethernet MAC and program it to hook up to a
> low power C8051 from silabs and put the fpga machine in a Actel
> smallest igloo fpga?

The small CPU jobs are certainly practical in small FPGAs, Jan's and
many others.  Opencores is riddled with them.  But for the motherboard
concept that started this discussion, I think people would be interested
in something beefier.

   - Larry


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