4004/8008 (was Re: Forgotten PC History)

[Ethan Dicks]

On Mon, Aug 11, 2008 at 08:29:28AM +0100, Pete Turnbull wrote:
> On 11/08/2008 07:37, schwepes at moog.netaxs.com wrote:
> 
> >The 8008 was only introduced a year after the 4004 which was
> >introduced in 1971.  I can't find a pin out for either of them
> >but I suspect that they might be pin compatable...
> 
> Not even close, I'm afraid.  The 4004 is a 16-pin device with Vdd (-10V) 
> and Vss (+5V) on the centre pins of the two sides, the 4 data bits on 
> pins 1-4, and the two clock phases and SYNC on pins 6-8.  The 8008 is an 
> 18-pin device with Vcc (+5V) and Vss (-9V) on diagonally opposite 
> corners (pins 1 and 10), D0-D7 on pins 2-9, and the clock phases and 
> SYNC on the other side (pins  14-16):
> 
> 	       4004			 8008
> 	      __ __			__ __
> 	  D0 |  U  | CMRAM0   (-9V) Vss |  U  | INT
> 	  D1 |     | CMRAM1	     D0 |     | READY
> 	  D2 |     | CMRAM2	     D1 |     | phi1
> 	  D3 |     | CMRAM3	     D2 |     | phi2
>  (+5V) Vss |     | Vdd (-10V)	     D3 |     | SYNC
> 	phi1 |     | CMROM	     D4 |     | S0
> 	phi2 |     | TEST	     D5 |     | S1
> 	SYNC |_____| RESET	     D6 |     | S2
> 	  			     D7 |_____| Vcc (+5V)
> 

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.

-ethan

-- 
Ethan Dicks, A-333-S     Current South Pole Weather at 11-Aug-2008 at 08:50 Z
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Ethan.Dicks at usap.gov            http://penguincentral.com/penguincentral.html