semi-homemade micro

Allison ajp166 at bellatlantic.net
Mon Nov 14 18:27:53 CST 2005


>
>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:
>
>> Jim Battle wrote:
>> 
>>>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
>> 
>> 
>
>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."

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




More information about the cctech mailing list