Intel 4040 - was Intel 4004 simulator and tools

From: Eric Smith <eric_at_brouhaha.com>
Date: Wed Feb 10 16:19:59 1999

Sam wrote:

> The 4040 was, I think, a whole
> different design by a different team inside Intel.

Maybe so. But the Pentium and Pentium Pro were designed by a whole different
design team inside Intel, and they seem to be fairly compatible.

If you look at the 4004 and 4040 data sheets, you will find that it has:

        The same instruction set, with a few additions
        The same register arrangement, only with more of them
        The same bus, but with more memory select lines

What it doesn't have is the same pinout. It's not a drop-in replacement
for the 4004. But then, the 8008 isn't a drop-in replacement for the 4004
either, and the 8080 isn't a drop-in replacement for the 8008. On the
other hand, if you wire up a simple adapter, you can put the 4040 in a
4004 system and it will work fine as long as the firmware doesn't depend
on illegal 4004 opcodes or non-existent registers.

On the other hand, when you compare the 4004 and 4040 data sheets with
the 8008 data sheet, you find that they have

        Entirely different instruction sets
        Entirely different register sets
        Entirely different memory architecture

> I'll have to find my notes I guess.

I'm certainly interested in what Ted Hoff has to say about it, but if he
wasn't actually on the 4040 team, then he isn't necessarily an expert on
it. I don't know any of the details of how these parts were designed,
other than what's in the published accounts, but I know how to read
data sheets.

Eric
Received on Wed Feb 10 1999 - 16:19:59 GMT