One of the 4's was for the bus size. It was a multiplexed
synchronous bus. It had 8 phases. 3 were for address and
one was for the rom. One or two were alu and I don't recall
what the other was for but I think it was bank selects.
Each device would watch the instruction and would do the
right thing ( I/O or RAM ) when it's time came around.
One might call it smart I/O. This way, the processor didn't
have to have the additional pins to select the function
for the bus.
Dwight
>From: "Sellam Ismail" <foo_at_siconic.com>
>
>On Thu, 16 May 2002, Tony Duell wrote:
>
>> I find that hard to believe. The 4004 was part of a chipset containing
>> the 4001 (ROM), 4002 (RAM) and 4003 (I forget exactly what, some kind of
>> I/O?). The 4001 and 4002 parts were used in lots of 4004 or 4040-based
>> designs.
>
>And according to Ted Hoff, it was quite by accident that it ended up with
>part number 4004. Coincidence and all.
>
>Sellam Ismail Vintage Computer Festival
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Received on Wed May 15 2002 - 22:45:25 BST