FPGA tricks - Re: using new technology on old machines. Was: PDP-12 Restoration at the RICM

Toby Thain toby at telegraphics.com.au
Mon Jun 15 10:08:38 CDT 2015

On 2015-06-15 9:35 AM, Dave G4UGM wrote:
> I don't think it is over kill. If you want over kill try this:-
> https://www.youtube.com/watch?v=ALXax3Gydl8
> and FPGA implementation of the Baby or SSEM which had 32x32 bits of
RAM. The implementation uses around 1% of the Spartan 3E 1200K gates,
and that includes the logic to generate the VGA which is around 50% of
the circuit. I expect to get it on a 100K gate chip but that’s still

Speaking of VGA, you might like this:



> I am also aware how HARD baud rate generator chips are. Firstly you
need to know the multiplier, and then you need a crystal that can easily
be divided. I looked on E-Bay UK and the cheapest dedicated baud rate
generator was 10x the price of a Arduino Nano. Then I would need a
crystal and the other bits to make the generator. I would expect the
chip count on a dedicated baud rate generator board to exceed that of
the Nano. Of course it is not original, but an authentic board would
only use SSI TTL and where would one find that easily.
> I personally think it is an appropriate cludge that allows
> de-bugging
to continue and gives you time to work out what the best long term
solution would be.
> Dave

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