5 May
2025
5 May
'25
2:41 p.m.
On May 4, 2025, at 5:51 PM, Will Cooke via cctalk
<cctalk(a)classiccmp.org> wrote:
From all I have seen, Maurice Wilkes is considered the inventor of "microcode"
as we know it. In the linked paper from 1951 he uses the term
"micro-programme", so I think it is safe to say microcode was used in the same
way in the 70s as it is today, although surely some people used it for normal machine
code. I have seen examples of that, although none come immediately to mind.
https://www.cs.princeton.edu/courses/archive/fall09/cos375/BestWay.pdf
From what I understand, the Dutch computer ZEBRA (a Dutch acronym for "very simple
binary computer") by van der Poel is, in a way, a machine in which horizontal
microprogramming is the way that regular programs are written. I haven't looked at it
in detail but the impression I got is that it uses the horizontal microprogram approach of
controlling individual elements of the machine concurrently by the various fields of the
instruction word, rather than defining "normal" instructions that perform a
single conceptual action at a time. That machine actually predates the Wilkes paper.
https://en.wikipedia.org/wiki/ZEBRA_(computer) has more.
paul