microcoding a PC into a PDP-11 (was: RE: Classic Computers vs.

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Sat Sep 22 12:58:13 2001

From: Bob Shannon <bshannon_at_tiac.net>
>
>I understand your confusion here, but in this case there already is
something
>defined as microcode. Simply adding another layer of complexity does
not change
>the underlaying microcode that runs directly on the hardware, its still
the microcode
>of the engine. This underlaying microcode still implements the
instruction set of

>the physical CPU hardware.


Because what your calling a microcoded engine is really running as your
microcode
something that used to be called macrocoding. IE: your "microcode"
engine a Pentium
understands yet another lower level code (internal pentium microcode).

In the end what you have been decribing is emulation. If your pentium
drove hardware
that was <registers and ALU> say 36 bits wide and ran code to drive it as
say a KL-10A
then the pentium would be a fully macrocoded microengine.

It's does not say a Pentium running dedicated code to emulate any machine
in such
a way as to hide the pentium completely is not a useful device.


The terminology of microcomputers was laid down a long time ago and if
you change meanings or the application of said meanings you invoke
confusion.

Allison
Received on Sat Sep 22 2001 - 12:58:13 BST