4004 and IC history / was Re: Vintage computer photogallery
dkelvey at hotmail.com
Sat Oct 13 23:20:24 CDT 2007
> From: hilpert at cs.ubc.ca
> dwight elvey wrote:
>>> From: hilpert at cs.ubc.ca
>>> Regarding the 4040, I'm speculating as I've never dealt with one or come
>>> across the pinout, but I suspect the 4040 essentially integrated the
>>> 4004/4008/4009 into one larger package making it look more like a 'standard'
>>> microproc in terms of signals/interface (somebody correct me if I'm wrong).
>> No, it was just a 4004 with, as I recall, two more instructions.
>> It kept the 4004 multiplexed bus and connected to 4001's and 4002's,
>> just like the 4004.
>> As I recall, it had 4 times the address space with bank selects. I'd
>> need to look at the specs again to be sure.
> Thanks for the correction, but why was it in such a larger package?
> (4040 was a 28 or 40-pin package wasn't it?).
It had more select lines for a larger address space. I think it added
an Interupt and a single step as well. I believe that made up for the
rest of the pins. It also had TTL compatible pins for many of the signal
lines. I believe that required an extra power line as well. I recall that the
reset line had inverted logic sense but that didn't effect the pin count.
I recall that did cause problems for the UPP. The other chips still had
the original sense of logic. On the UPP, they'd used a transistor to
invert the level. The problem was that they'd released the CPU about
3 cycles befor releasing the ROM's reset.
It was flakey on reset. Some boards just never reset right.
They even had an ap note stating to put a few nops at the start
of the ROM to fix this. This didn't always work right. Changing the
reset order fixed it.
It seems the 4040 was a 24 pin part.
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