semi-homemade micro

[Allison]

>
>Subject: Re: semi-homemade micro
>   From: woodelf <bfranchuk at jetnet.ab.ca>
>   Date: Mon, 14 Nov 2005 13:14:09 -0700
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
>Don North wrote:
>
>> 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).
>>
>I would say it takes a few instructions since you have to mask for 12 
>bit words, and remember the PC is running windows and all
>sorts of other stuff. The point is the emulation is at least 6x faster 
>or more compared to
>the original.  Faster may not allways be better for emulation.

With a machine wider than 12 bits the mask is a single instruction AND.
The content of the subfields are more difficult than that but most of
x86s handle bits fairly well.

Allison