<are plain false). I'd not try to re-implement the PDP11 unless you had a
<good reason to do that -- rather, design an instruction set and
<architecture and implement it.
Good point. If you want a good -11, find one. Myself I find the 11
to be more of a software playground with that instruction set.
If I were doing my own, well then, it's a matter of what if...
I'd start with a 32bit PDP-8 (just add 20 more bits on the right side).
I'd keep the PDP-8 instructions (add a few more microcoded ones for byte
ops), addressing and IO. With 32bit addressing and 27 bits direct
addressing in both current page and page 0 it would make a good enough
graphics cpu to be useful, if fast. Even if scaled back to 24 bits it
would be interesting. Also very buildable using 74F parts. At the same
time old PDP-8 code could be "lofted" to run on it so a OS would be
possible in a reasonable time. With a little effort a .3us instruction
cycle is very doable (3mips!) maybe even faster. Pentium no, but fast
enough to make some sense.
Allison
Received on Thu Aug 26 1999 - 19:06:55 BST