On 23-Mar-20 14:36, Paul Koning wrote: > >> On Mar 23, 2020, at 1:29 PM, Timothe Litt <l...@ieee.org> wrote: >> >> ... >> On the VAX 730: as far as I'm aware it's the only VAX built out of >> standard LSI CPU components. The guts of the CPU is AMD 2901 >> bit-slice chips. All other DEC microprogrammed machines I can think >> of had their own purpose-designed logic.
The PDP-11s, like the 11/05 were ttl, the CPU ALU was something like 74181 4 bit slices. I don't count them as "real" microcoded machines for some reason - perhaps because the ucode was all ROM, and IIRC there was no assembler for it. The KS10 uses 2901 for its CPU - because of the 1/2 word arithmetic, it's actually 40 bits wide. The 780 is TTL. The 785 is the same machine, upgraded to 74S. The UDA data mover used 2901s so cleverly that it went into several more generations of disk controllers. It timeslices the 2901 such that it runs two programs - one on the A and one on the B phase of each clock cycle. > 2901 bitslices do appear in other DEC products, the UDA comes to mind. And > that has, for running on-board diagnostic tools, a small PDP11-like > instruction set implemented in a little bit of 2901 microcode. By Richie > Lary, wizard of compact software... > > paul >
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