https://en.m.wikipedia.org/wiki/Microcode
On Mon, Mar 23, 2020, 5:49 PM Ray Jewhurst <raywjewhu...@gmail.com> wrote: > Slightly off topic, could someone explain more about what microcode is and > how it works? The fact that the CPU instructions are they themselves > programmed in seems unfathomable. > > Ray > > On Mon, Mar 23, 2020, 5:33 PM Clem Cole <cl...@ccc.com> wrote: > >> >> >> On Mon, Mar 23, 2020 at 3:57 PM Johnny Billquist <b...@softjar.se> wrote: >> >>> The VAX-11/750 used 2901 though... >>> >> 750 was made out of custom CMOS gate arrays. The main adder was analyzed >> as part of my thesis [long story - not for here, but a very clever >> circuit. I would later get to know the guy that did it]. Paul Gilbeau >> and Dick Monroe were the main microcoders on the 750. I'm pretty sure that >> Paul was also one of the 780 microcode folks. Very interesting guy. I >> used to say he had a worm's eye view of the world -- perfect for his job as >> lead microcoder; but trying to get up a level could be difficult. I've >> lost track of them both, although I still talk to Dave Cane a couple of >> times a year and I think he knows how to find most of the HW team. >> >> I'm fairly sure that the 750 used te BLISS based Micro2 tools as Tim >> suggested and as I said, we cloned them at Masscomp in C (which later it >> went west). Tim, you tell me, I thought the Masscomp version got sent to >> the Jupiter team, but I'm pretty sure it was used for Prism. I remember us >> getting a 'bug report' because VAX-11/C didn't like something BSD's yacc >> had generated at one of the Hatfield/McCoy parties. I remember changing >> what it was and email it the next day. >> >> FWIW: All of the Masscomp FP/AP and the DACP used that set of >> microcode tools since they were all AMD 29xx based. IIRC, Chuck Palmer >> overhauled the original hack we did for Paul and Dick because a few Masscomp >> customers wanted to write custom DACP microcode and originally it was >> not too easy. I probably have a manual for that still around and maybe >> even the tools. But, since I don't have a DACP on the MC500 I still >> have, I never bother scooping up the tools. >> >> Also, I know that there was an Intel 808x processor (85 I think) that >> shipped in the 750, but it was not an FEP. It was limited to running the >> cartridge tape controller. I don't remember how the console serial port >> was done (the 780 it was part of the FEP). The 750 microcode did the boot >> as someone else pointed out. I've forgotten how the microcode was loaded >> on a cold start. I thought there was something in a ROM/EPROM, but I've >> forgotten. I do know the cartridge tape unit was needed to update the >> microcode and that was the only way to do it. But I don't remember you >> need to have the tape on a cold reboot the like floppies on a 780, but I >> could have forgotten. >> _______________________________________________ >> Simh mailing list >> Simh@trailing-edge.com >> http://mailman.trailing-edge.com/mailman/listinfo/simh > > _______________________________________________ > Simh mailing list > Simh@trailing-edge.com > http://mailman.trailing-edge.com/mailman/listinfo/simh
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