PDP-8 on FPGA project & where is Hans Pufal?

bfranchuk at jetnet.ab.ca bfranchuk at jetnet.ab.ca
Fri Dec 19 00:19:59 CST 2008


Philipp Hachtmann wrote:


> To be clear:
> My PDP-8 currently does 50000000 additions/second. Or 100000000 operate 
> or jump instructions/second.

Well that does make it the fastest 8 on the planet.

> Best wishes,
> Philipp

I am lucky if I can get normal memory speeds ( min 1970's )  with my CPLD design
but most the problem is that I have to use slow I/O chips. I don't use pipelining
with my design so I figure I have about 4 gate delays for control signals, 4 
gate delays
for datapath logic and 4 x 2 gate delays for carry to ripple.  With the cheap 
chips I have
( 20 ns delay ) I have no problem with creating a computer up to 2 Mhz ... nice 
and slow
but it does fit my goal what  cpu that is not 8 or 12 bits wide on the data path.
The 20 bit cpu alas can't be a (fictional) single chip cpu since I can't fit it 
into a 48 pin dip.
I am two pins extra. [1]
Ben.

[1] They are inputs so I might be able to multiplex them in but it is messy.




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