4 May
2025
4 May
'25
10:05 p.m.
The IBM5100 also uses the term "microcode" - but I'm not sure if that term
pre-1975 means the same as what, say, Intel used it for around the x86?
I've seen a glimpse into the syntax of the x86 microcode. In the IBM
5100's case, its CPU is distributed across 14 or so SLT chips - so I never
fully understood how it implements its PALM instruction set. I know the
two large IC on that process are two 64-byte memory things (dunno if
categorized as SRAM or DRAM, or neither), mapped to the first 128 bytes of
system RAM (so a high speed pass through, where that 128 bytes correspond
to the registers used by each of the 4 interrupt levels). That PALM
processor was developed right around the time of the Intel 4004 (late '71 /
mid '72), and stout enough to run a version of APL about a year later (I
see Intel made a version of FORTRAN for the 8008, or at least a claim for
it in the Intertec brochures).
Anyway, all I mean is, in early 70s did "microcode" just mean
instruction-set, and that changed a few years later? Or did microcode
always mean some kind of "more primitive sequence" used to construct into
an instruction set?
-Steve
On Sun, May 4, 2025 at 1:33 PM ben via cctalk <cctalk(a)classiccmp.org> wrote:
On 2025-05-04 2:11 a.m., jos via cctalk wrote:
Well for BASIC that is true.
The Fairchild Symbol Computer was test to just how far TTL could go.
> I recall that system had many boards, the
whole "CPU" box was external
to
the
monitor (and in the earliest versions, the power supply was also a
large external box). I can't really fathom creating a BASIC out of raw
TTL, or maybe I'm misunderstanding the approach.
You build a processor with some TTL, and then implement a BASIC on that
microprocessor.
There is always this intermediate step, no machine executes BASIC
directly in TTL.
Look here for an example of a processor
(Datapoint 2200) in TTL :
https://bitsavers.org/pdf/datapoint/2200/jdreesen_shematics/DP2200_mb.pdf
Jos
Micocoded coded machines, could likely be programed to run basic.
Ben.