31 Dec
2008
31 Dec
'08
11:03 p.m.
Chuck Guzis wrote:
...
Well, the Burroughs B5000 was purportedly an Algol
machine; there
have been CPU designs to eat UCSD Pascal bytecodes and Java bytecodes
and there have been various LISP machines. But none, AFAIK, to
actually lexically parse program text input in hardware. I suppose
1401 Autocoder might be in that league, if you consider Autocoder to
be a "language".
I remember reading a computer architecture book back in the early/mid 80s, I think it was
by Stone. The subject was "advanced" architectures. One section described on
attempt to
build a timesharing system for running a BASIC-like subset, and everything was hardwired
-- parsing was via gate-level state machines, not microcode. The intended audience was
college-level computer classes. As I recall, they gave up after getting a simplified
version going.
I believe that Intel actively discouraged programming
in assembly on
the i860, given the mind-bending instruction scheduling issues.
The exposed pipe hazards weren't the real issue. The problem was exceptions. In
certain
states, there was no simple way to restore the pipe, so the interrupt handler had to
detect when one of those bad cases existed, then nudge the state along one instruction at
a time until it go to a point where it could restore the state fully and really return
from the interrupt.
I never saw it, but I heard the return from interrupt code was a couple thousand lines of
tricky assembly.