[vcf-midatlantic] Working on a historical microprocessor exhibt

[David Riley]

On Feb 9, 2020, at 14:25, Dave McGuire via vcf-midatlantic <vcf-midatlantic at lists.vcfed.org> wrote:
> 
> On 2/9/20 2:02 PM, Adam Michlin via vcf-midatlantic wrote:
>> Ooo.. how could I forget Fairchild? Thanks!
>> The AMD bit slice is new to me. Am I understanding correctly that it is
>> not a discrete CPU but rather parts of a CPU that could be used
>> together? Probably not a candidate for this exhibit, but I'm already
>> having ideas for the next one!
> 
>  Bit-slice is great stuff.  There are many bit-slice chips, but the
> Am2901 essentially owned the market.  It is a four-bit unit.

Yes, the Am2900 family is the quintessential bit slice series. It’s 4 bits wide and comprises an ALU, sixteen registers and carry-lookahead generation inside, and it’s FAST for the time. Coupled with a carry generator and some fast bipolar PROM or SRAM for the control store, you could make a whole 16-bit processor running at 16 MHz (maybe 20 if you pushed it) in just a handful of chips.

You don’t need the 2910, either, it’s mostly just a convenience chip. Learn how to build a processor with Am2900 logic, some PROM and some registers, and you’ll forever understand that a CPU is nothing more than a fancy state machine.

- Dave