On Mon, 10 Dec 2001, Ben Franchuk wrote:
I wanted to do
it old because I actually own a first-revision PDP-11/70
which my father bought brand new back in the mid-70's when it first came
out before I was born. It's a really really neat machine with gobs of I/O
bandwidth. It's fast too. So it made me think what I might be able to do
with modern components and still make it compatible with my 11/70. (FYI,
my 11/70 is still working and is still original, down to its fuses and
fascia).
Building my 'prehistoric' CPU, I have discovered I am about 5 years
too late to find TTL. 16 x4 RAM and ALU's are very scarce and never
produced in the newer families. You may still find stuff in 74Fxx but
you still are only about 1/2 the power. I am assuming the 11/70 used
74Sxx. You can do a lot with FPGA's today but I don't expect a full
grown PDP-11 will fit in a fpga that is not in a 144 pin TQFP package.
Funny how the logic is now 'super large' FPGA's and single gate
'glue'
chips.
Yeah. I wasn't actually trying to build it using any specific technology.
What I am doing is taking the latest and greatest and building a PDP-11
compatible (one that act's *exactly* like an 11/70, but faster). I am
probably not going to be using FPGA's, because I don't think they're yet
making FPGA's the speed I want them to go.
Peace... Sridhar