semi-homemade micro

[Don North]

Doing some math, 2GHz/100KHz is 2000MHz/0.1MHz or 20,000. At 6X the 
cycle count is then 20K/6 = 3333 (not 3.3M).
One would think it takes well less than 3000 X86 instructions to emulate 
a PDP-8 instruction (assuming one instr per clock).

Jim Battle wrote:

> woodelf wrote:
>
> ...
>
>> Having got a new PC ... 2 GHZ???  who knows the real speed.
>> I have tried Spare time gizmos - pdp 8 emulator  ( A minor bug
>> -- with windows  how do you get the bell to sound ?).
>> I was running some sort of diagnostics and had the RTC displayed
>> and for about 10 minutes of real time, the clock advanced a hour.
>> That must be at least 6x faster than the real thing on this computer.
>
>
> If a 2 GHz (give or take) x86 CPU emulates a pdp 8 at 6x, it means 
> either the code is inefficient, or the code contains a speed regulator 
> that doesn't work properly.
>
> The original PDP-8 took 10 clocks at 1 MHz to execute one instruction, 
> a 2 GHz CPU has 20 million cycles to interpret one instruction.  So at 
> 6x realtime, the program is using 3.2 million cycles to interpret one 
> instruction.
>
> Most likely speed and efficiency weren't goals of the emulator, so I 
> bring this up not to discredit the program's author but rather to say: 
> don't use that data point as anything but a lower limit on what kind 
> of horsepower it would take to use a micro to emulate a PDP-8.  I 
> imagine an AVR device at 20-40 MHz should be able to emulate a PDP-8 
> at real time.
>
>
>