Lisp, the machine language. Was Re: Hallelujah!

From: ss_at_allegro.com <(ss_at_allegro.com)>
Date: Tue Apr 6 13:30:39 1999

William writes:

> My wish is for a computer system that provides for dynamically modifiable
> microcode, so that my self-modifying programs could obtain a new level
> of self-modifyability!

Ah..a few decades too late :)

The Burroughs B1700 (and B1800 and B1900) could have been
used that way, I suppose. The machine had multiple microcode
sets, executed by picocode. (IIRC, Picocode was written in an
ALGOL-like language)
I don't recall seeing any particularly protection mechanism that
would have prevented you from modifying a microcode on the fly.

The COBOL compiler determined which microcode to use, based on
things like the number of variables used by the program being
compiled. (If a program used a small number of variables, it could
be compiled to a microcode instruction set that had more compact
instructions because the number of address bits was smaller.)

Another microcode instruction set was used for the primary OS
programming language (SPL? XPL? can't recall). I seem to recall
several other microcode sets being around as well.

When processes were "time sliced" (multi-programming), the
microcode was also time sliced. (I.e., process A might be using one
microcode, while "simultaneously" process B might be using a
different microcode).

> As for the Lisp difficulties, remember, it takes only a few of the basic
> operators to define the language. All else can be derived from same,
> and AFAIK is derived from same. So, there is no need to implement
> derivable functions in microcode.
>
> William R. Buckley
>
Received on Tue Apr 06 1999 - 13:30:39 BST