[Simh] Is it possible to simulate the first Vaxen I ever used?

[Gregg Levine]

Hello!
I agree with you Tim, that's an excellent book on the subject.
The AM2901 was used in some DEC designs that I know of. In fact in the
databook I have here, AMD mentions that some part numbers were
themselves designed for those DEC designs. And that some LSI-11
designs found themselves fully built using the AM2901. The sequencing
parts that the company made were in all probability not used inside
them. But were used elsewhere.

Oh and some of the DEC designs did also use the Series 74 ALU ,the
SN74181 one. I remember that from some reading about the entire design
process. In fact that TI ALU is itself a complex part, perhaps almost
as complex as the 74S481 that Mentec would attempt to use many years
later.
-----
Gregg C Levine gregg.drwho8 at gmail.com
"This signature fought the Time Wars, time and again."

On Mon, Mar 23, 2020 at 6:06 PM Tim Shoppa <tshoppa at gmail.com> wrote:
>
> The Mick and Brick book is THE BEST and 100% applicable to the 2901-based  11/730 and KS discussions here. http://bitsavers.org/components/amd/Am2900/Mick_Bit-Slice_Microprocessor_Design_1980.pdf
>
> On Mar 23, 2020, at 5:49 PM, Ray Jewhurst <raywjewhurst at 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 <clemc at ccc.com> wrote:
>>
>>
>>
>> On Mon, Mar 23, 2020 at 3:57 PM Johnny Billquist <bqt at 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.
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