4004 and IC history / was Re: Vintage computer photogallery

Ethan Dicks ethan.dicks at gmail.com
Sat Oct 13 19:32:35 CDT 2007


On 10/13/07, Roy J. Tellason <rtellason at verizon.net> wrote:
> On Saturday 13 October 2007 15:40, dwight elvey wrote:
> > > > 4008/9? First I've heard of these at all.
> >
> >  These were but interface chips that took the pmos levels and convertered
> > then to TTL levels to use with standard RAM, ROM, EPROM and I/O.
>
> Oh,  heck,  I'd forgotten about PMOS stuff altogether!   :-)

Hmm... PMOS... I know that there are fundamental composition and
voltage differences between NMOS, PMOS, CMOS, HMOS, etc... What makes
it not-compatible with TTL (unlike CMOS, which is easy to interface to
TTL)?

>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.

-ethan



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