4004 and IC history / was Re: Vintage computer photogallery

[Brent Hilpert]

Ethan Dicks wrote:

> >From time to time, I consider building a small 4004 board - nothing
> more complicated than a digital clock, but my lack of examples to
> study in detail always slows me down.  I've read over various
> datasheets, but not recently enough to really recall any specifics.  I
> happen to have a couple of 4004s already - one plastic, one ceramic
> package, but they came from devices that I didn't have schematics for
> (one digital kitchen scale, one early barcode reader), and don't have
> the original PCBs from to study.
> 
> I can't say that a modern 4004 project would be practical, but it sure
> would be neat to watch.  I know there were some older bi-polar 4-bit
> PROMs that should still be programmable with 25-year-old programmers,
> but I suppose that it's just easy enough to use modern 8-bit devices
> and ignore 4 of the bits.

I think one essentially has two choices:

  - find a 4008 & 9 to break out the bus and then you can use standard
    8-bit EPROMS (4004 instructions are 8-bits actually). You may still
    be screwed for RAM without a 4002 though, as the 4004 is Harvard arch.
    and I'm not sure that the 4008/9 bring out the data address space.

  - (re)design some bus muxing logic (4000 series CMOS should interwork)
    to deal with the 4004 cycle and use 4 or 8-bit (E)PROMs and RAM.
    In other words, recreate the 4001 and 4002 in SSI (or 4008/9 depending
    on your perspective).

(For 4004 stuff it's nice to find equipment with at least the entire digital
portion intact, precisely to avoid having to do the above.)

(And I forgot to mention the 4201 clock generator (still looking for one)).