Date:         19951025
From:         Max
Organization: Intergraph Electronics
Newsgroups:   sci.electronics
Subject:      Re: 4040: early CPU?

Mark Zenier writes:
>John Lundgren wrote:
>: Augarten's "Bit by Bit" history of computers says that Intel went from
>: the 4004 to the 8008 in April of 1972.  So maybe the chips you have are
>: not uPs.
>
>There are better history books than that.  Try "Computer Structures:
>Principles and Examples".  As I remember reading it, there was quite a
>bit of overlap between the 4004 and 8008 projects.  The 8008 was out a
>year after the 4004 but both were in progress at the same time.  The
>4004 was for calculator cpus for Busicom, and the 8008 was for an
>intelligent terminal for the company that later became Datapoint.  (Who
>didn't use it for speed reasons.)
>

I agree, the 4004 was the first - it has a 4-bit wide data field and
a 12-bit data field, but the address and the data were multiplexed
on the same 4-bit bus. So, to perform a simple memory write, the
device wrote three 4-bit groups to build the address (which was 
latched outside the device), then wrote the 4-bit data (package
pins were expensive in those days).

The 8008 came next and it was essentially an 8-bit version of
the 4004 and the two ran in parallel for a while. Then they
brought out the 4040 which had some logical operations added
to it's ALU and also an internal stack (I'm running on memory
here but something like seven or nine words each 12-bits wide),
then the 8080 came out, then .... the field exploded with 6800s,
6502s, Z80s, and loads of others.

Cheers - Max
web: http://iquest.com/~virtual/max/bebop.html