14 Nov
2005
14 Nov
'05
4:27 p.m.
Subject: Re: semi-homemade micro
From: Jim Battle <frustum at pacbell.net>
Date: Mon, 14 Nov 2005 17:57:08 -0600
To: General Discussion: On-Topic and Off-Topic Posts <cctalk at
classiccmp.org>
Brad Parker wrote:
That just doesn't sound right.
The 8E which I'm most familiar with is considerably faster than that. Though
the 8S would be slower. I dont consider wikipedia expert here. Doug Jones
and a slew of others have far more complete and accurate sites. Though the
DEC handbooks are not to be trifled with either.
Allison
Jim Battle wrote:
I'm no PDP-8 expert. My source was this web page:
http://fixedreference.org/en/20040424/wikipedia/PDP-8
"The PDP-8 was a 12-bit computer with 4096 words of memory. It had only eight
instructions, one full register, the accumulator (AC), and a single-bit
register, the link (L) bit. The machine operated at a clock rate of 1 MHz, and
took 10 clocks for each instruction, so that it ran at 0.1MIPS." The original PDP-8 took 10 clocks at 1 MHz to
execute one instruction
really?
I'm probably off, but at a cocktail party I would would have said that
some instructions took 8 clocks (f0,f1,f2,f3,e0,e1,e2,e3) and some took
12 (f0-f3, d0-d3, e0-d3).
That's according to a recent look at the "blue book", but I may have
misunderstood. I did write up some verilog which uses those states and
it seems to be (mostly) correct, but it's done all debugged yet.
-brad