8008 v. 4004... & what was the second COTS microprocessor?
mc at media.mit.edu
Tue Dec 16 13:11:49 CST 2008
From: Paul Koning <Paul_Koning at Dell.com>
Subject: Re: 8008 chips / RAM's
Jos> ...The i4004 is a controller, at least to me, because it is
Jos> dependent on a specific set of supporting ciruits (4001,40002
Jos> and 4003). The 8008 is much more general purpose.
I would make the distinction on the basis of what you can do with it.
A college classmate of mine built a 4004 based microcomputer in 1974
that was a general purpose machine, just as the early 8008 basd
micros. I would certainly call his creation a microcomputer, not a
controller. It certainly was hairy -- about 100 chips on a large
wire wrap board.
Sure, I could imagine agreeing that the 4004 was a "controller," but these are just names. It is still a microprocessor, just that it had a very convenient bus architecture that let you connect RAMs, ROMs, and I/O with no "glue logic." It is certainly true that the bus interface of the 8008 was more general than the 4004, but this meant that the 8008 required dozens of support chips just to build the most minimal system. Peripherals and memory each required decoders to partition the bus address space, whereas the 4001 and 4002 had built-in decoders. It is worth noting that eventually the 4008, 4009 and then the combined 4289 came along to allow the 4004 (and the 4040) to interface to standard memories (static RAMs and e.g. 1702 PROMs). Alas, the 8008 didn't last very long, whereas the 4004 had a 15-year manufacturing run, even as the space of 8-bit microprocessors exploded and surpassed the meager 4004 in capability. The 8008 was originally purpose-built to be a terminal controller and then released for general use.
People make a big deal about the first-this and the first-that, but then what happens is no-one can remember the second-this and the second-that. Can anyone remember what the second commercial, customer-programmable microprocessor to hit the market? The 8008 came out in 1972. Were there others introduced that year? I know that the TMS-1000 was right around that time.
More information about the cctalk