[vcf-midatlantic] Working on a historical microprocessor exhibt

Ben Greenfield ben at cogs.com
Tue Feb 11 10:57:53 EST 2020

What I think is funny about this topic is that my whole collection is based around the processes used to form the technology.
The logic is all consistent and more or less solved but the implementation into ever smaller/more widely accesible forms is what I find interesting.

> On Feb 9, 2020, at 2:58 PM, Adam Michlin via vcf-midatlantic <vcf-midatlantic at lists.vcfed.org> wrote:
> On 2/9/2020 2:24 PM, Dave McGuire via vcf-midatlantic wrote:
>>   Bit-slice is great stuff.  There are many bit-slice chips, but the
>> Am2901 essentially owned the market.  It is a four-bit unit.
>>   Basically it's a processor building block used to construct a
>> micromachine.  You stack them up to whatever bit width you want, and
>> program them with microcode to implement whatever macro-architecture you
>> want.  There are companion chips, like the Am2910 sequencer, etc.  These
>> are not required but come in handy.  The sequencer can implement
>> constructs like a microprogram counter, branches and jumps, etc.
>>   A few examples you've heard of: The VAX-11/730 uses a row of eight
>> Am2901s to implement a 32-bit VAX processor, and the DECsystem-2020 uses
>> a row of nine to implement a 36-bit PDP-10 processor.  Both use
>> RAM-based control stores, so when they power up they don't speak the
>> VAX/PDP-10 instruction sets until after the microcode is loaded.
>>   This is generally the smallest/cheapest approach to build a large
>> processor.  The VAX-11/730 and DECsystem-2020 are very small, very
>> low-end members of their respective families.  But the bit-slice chips
>> themselves are quite fast for their day, being big hot-running 1970s
>> bipolar chips.
>>   It's also possible to use Am2901s (or other bit-slice chips) as
>> processors in their own right.  For example, many, many third-party disk
>> controllers for DEC machines use a pair or a quad of Am2901s to
>> implement their functionality.  In this application they typically
>> aren't running microcode, but are used as more of a microcontroller with
>> firmware.  The distinction is largely semantic, though, of course.
>>   It's great stuff.  If you want to learn more about how all of this
>> works, I recommend picking up a copy of "Bit-Slice Microprocessor
>> Design" by John Mick and James Brick.  This book is/was known in the
>> industry as "Mick & Brick".
> That fills a huge hole in my understanding of architecture history. It certainly makes sense that there would be separate ICs that eventually merged into one discrete CPU. I just assumed it was done by the minicomputer manufacturers themselves. I had no idea it was AMD! Thanks!

This is the area where I think the Autonetics created a series of artifacts that really tells a good story about the process moving through discrete components to mos to mos-lsi.

The Autonetics D17B was a pre-lithographic process real time computer.

Each board looked sort of like this


Then as far as I can tell Autonetics developed the process to use a photo-lithographicly re-produce the previous generation technology.

the block on the top of the picture was a lucite desk ornament showing the number of discrete parts fit in it’s new chips


This picture shows the back of the block which has diagram of circuit that was used in the 1962 board.
The sales notes are on the back of the sample kit

which is opened in this photo


For me when the topic of microprocessors comes up I always marvel at the trial and error/ out of the box thinking which uses the same logic in smalller forms.

There are many ways to slice this onion,


>>> I'd love to find a Zilog Z8000, but don't imagine period correct Z8000s
>>> are so easy to come by. We have a Z8000 machine in the warehouse, but
>>> one of the big rules for this product is that no vintage computers will
>>> be harmed to make it happen.
>>   Are you talking about just a Z8000 chip?  I can provide that for the
>> exhibit.  It will need ESD protection, of course.
> Cool, we'll talk. And not only ESD protection, but non degradable ESD protection is being planned.

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