4004/8008 (was Re: Forgotten PC History)
dkelvey at hotmail.com
Mon Aug 11 09:08:43 CDT 2008
> From: ethan.dicks at usap.gov
> Hmm... I happen to have a couple of 4004 chips (one pulled from a
> non-UPC barcode scanner, the other from a commercial kitchen scale),
> and I've long fantasized about building some showcase 4004 circuit,
> probably a digital clock.
> I don't happen to have the 4004 datasheet handy (and can't get to it
> for a number of hours), but the -10V Vdd requirement makes me wonder
> if it's possible/feasible to use a pair of ganged ICL7660s (still made
> by Dallas/Maxim) to generate it. This chip came up recently as a
> possibility for generating -5V Vdd for 4116 DRAMs (and I think the
> concensus was that it would probably be adequate for up to 16 chips),
> so I do recall that it can only source a few mA (each 4116 needs a
> few dozen uA)...
> I don't see a GND pin on the 4004, so I'm at a loss to estimate
> what it would require for Vdd. Anyone know or can check easily?
> Also, does anyone know about any sort of 4004 emulator or simulator?
> I wouldn't mind trying my hand at some code *before* trying to build
> out the hardware.
The chip is P-mos and it doesn't directly connect to ttl.
The down is very week and only pulls up with any
There were a couple chip interfaces ( 4008 and 4009 )
that created TTL level signals to run standard RAM/ROM.
The only issue here is that one lost the instruction stream
so that one couldn' t take advantage of any RAM ot ROM
The later came out with a single chip version of the
interface( I think it was 4269 ).
These come up on ebay every now and then.
The manual on Al's site shows a circuit to convert the Pmos
levels to a TTL eprom ( used on the SIM4-1 ). The circuit does
use 4002-1 and 4002-2 RAMs.
The 4001/4002 had built in I/O. They would watch the instuction
steam and execute an I/O operation when the 4004 executed
the fetched instruction.
It is easier to modify a -12V supply to power the -10v than
to make a converter. Many floppy disk supplies are fine for
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