7 May
2025
7 May
'25
11:54 a.m.
Steve
Thank you for the link to Shrriff (below) - interesting and with valuable references,
including from the commentariat
Folks
Two microprogramming URLs worth following up - both pdfs
https://ed-thelen.org/comp-hist/MicroprogrammingABriefHistoryOf.pdf 2012 commentary on
microprogramming
https://baltazarstudios.com/webshare/A-Z80/Library/Demystifying%2520Micropr…
Z8000 design retrospective
Enjoy
Martin
-----Original Message-----
From: Steve Lewis via cctalk [mailto:cctalk@classiccmp.org]
Sent: 07 May 2025 05:50
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Cc: Steve Lewis <lewissa78(a)gmail.com>
Subject: [cctalk] Re: Wang TTL BASIC
For reference, Shirriff describes aspects of the 8086 microcode here How the 8086
processor's microcode engine works
<https://www.righto.com/2022/11/how-8086-processors-microcode-engine.html>
https://www.righto.com/2022/11/how-8086-processors-microcode-engine.html
Including a reference to 1951 Wilkes concept.
As the S/360 used microcode, I'm suspect if PALM used some form of microcode (which
was developed at or near Boca Raton c.1971, but not much is known about it -- we have its
instruction set documented as early at 1972, and the "M" is PALM is said to be
Microcode). Just unclear what they really had going on in those SLT modules.
But back on the original Wang question: I still can't find high resolution images of
it's CPU board. According to 1991 discussion here on the 2200B, there is also mention
of the system not really having an instruction set, BASIC was all it could do since it was
"hard wired."
https://groups.google.com/g/alt.folklore.computers/c/lb0DzzDja-Y
I would think by 1991 they knew what a ROM was and would have called it as such, so
I'm still curious if we have right on how that system worked.
People may have had that impression about the IBM 5100, but we've showed it has a DSP
(kind of diagnostic mode) where you code in PALM machine code (or even load "binary
blobs" of previously stored PALM code onto tape [ video on it here, towards the end I
load an IBM 5100 ported version of Corti's original one he did for the 5110
https://www.youtube.com/watch?v=e2GYWyZyfpE
]), and the earliest PALM instruction docs we have is from 1972. That doc doesn't
describe how many cycles each instruction takes, but I think in the IBM 5100 SLM docs it
does imply they have a variable number of cycles.
On Mon, May 5, 2025 at 4:18 PM Brian L. Stuart via cctalk < cctalk(a)classiccmp.org>
wrote:
On Mon, May 05, 2025 at 04:09:29PM +0100, David Wade
via cctalk wrote:
I think "Microprogramming" as a
technique has been around as long as
we
have
had computers. Couldn't the setting up ENIAC
to behave like a stored
program
computer in 1948 be described as
"Microprogramming"?
That's an interesting question, but I'd say yes. I base that on the
idea that microprogramming is essentially programming one universal
machine to emulate another universal machine with the purpose of using
the programming model of the second machine as one that is more
convenient than that of the first. Of course, it doesn't look at all
like the microprogramming we're used to, but I'd say it still applies.
> The Zuse Z1 from 1936(!) was microcoded,
too. It implemented for
example
> floating-point arithmetic and conversion
instructions
> (binary<-->decimal).
>
> Christian
I'd add that we can go back even farther. Babbage included a
mechanism on the analytical engine for the more complex operations
that was effectively microcode. I was implemented with a cylinder
(referred to as a barrel) that you could screw blocks into. A set of
levers were pressed against a line of block positions along the length
of the cylinder and the presence or absence of a block would determine
whether the connected mechanism is engaged. Then the cylinder is
turned one step and the process repeated. The whole thing ends up
being a lot like typical horizontal microcode.
BLS