12 Dec
2012
12 Dec
'12
1:48 p.m.
On Dec 12, 2012, at 15:40, ard at p850ug1.demon.co.uk (Tony Duell) wrote:
11/730. To fit a VAX processor onto 3 hex-heightcards
using only stnadard
ICs [1] is a hack. It;'s postly (unprotected) PALs. There are 8 MA291s
for the ALU. The really stupid bit of design, and the boatie who came up
with this needs a touch of the clue-by-four is that the microcode store
is _DRAM_. Yes, you read that right. 4116s IIRC. The problem is, of
course that the execution of the micorocde doens't access all locations
in the store quickly enough, so the RAM is not autometically refreshed.
You guessed it, the CPU is paused every so often asd the control store
is refreshed. That's one thing that slows it right down. Why they didn't use
SRAM is beyond me....
Link error: unresolved reference ([1])