Comment by adrian_b | Hacker News Reader

Comment by adrian_b | Hacker News Reader

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Very impressive work, but most of the work has been necessary because Intel 4004 was not really the first microprocessor, this was just BS propaganda used by Intel to push back by one year the date of the launch of the first microprocessor, to 1971.

The first true (civilian) microprocessor was Intel 8008, in 1972.

Intel 8008 was a monolithic implementation, i.e. in a single PMOS integrated circuit, of the processor of Datapoint 2200, therefore it deserves the name "microprocessor".

The processor of Datapoint 2200 had an ugly architecture, but there is no doubt that it was a general-purpose CPU and traces of its ISA remain present in the latest Intel and AMD CPUs.

On the other hand, the set of chips that included Intel 4004 was not intended for the implementation of a general-purpose computer, but it was intended just for the implementation of a classic desktop calculator, not even a programmable desktop calculator.

This is the reason for the many quirks of Intel 4004, e.g. the lack of instructions for the logic operations, and many others that have increased the amount of work required for implementing a MIPS emulator suitable for running Linux.

Even if Intel 4004 was intended for a restricted application, after Intel has offered to sell it to anyone, there have been many who have succeeded to use it in various creative ways for implementing microcontrollers for the automation of diverse industrial processes, saving some money or some space over a TTL implementation.

In the early days of the electronics industry it was very normal to find ways to use integrated circuits for purposes very different from those for which the circuits had been designed. Such applications do not make Intel 4004 a true microcontroller or microprocessor. Very soon many other companies, and later also Intel, have begun to produce true microcontrollers, designed for this purpose, either 4-bit or 8-bit MCUs, then Intel 4004 has no longer been used for new designs.

I'm glad to see the Datapoint 2200 is getting attention, but by reasonable definitions of "microprocessor", the Intel 4004 was first, the Texas Instruments TMX 1795 was second, and the Intel 8008 was third. It seems like you're ruling out the 4004 on the basis of "intent" since it was designed for a calculator. But my view is that the 4004 is a programmable, general-purpose CPU-on-a-chip, so it's a microprocessor. Much as I'd like to rule out the 4004 as the first microprocessor, I don't see any justifiable grounds to do this.

Intel's real innovation—the thing that made the microprocessor important—was creating the microprocessor as a product category. Selling a low-cost general-purpose processor chip to anyone who wanted it is what created the modern computer industry. By this perspective, too, the 4004 was the first microprocessor, creating the category.

My article in IEEE Spectrum on this subject goes into much more detail: https://spectrum.ieee.org/the-surprising-story-of-the-first-...

Your argument is that because the 4004 was built to power a calculator that disqualifies it as a microprocessor? Independent of the actual nature of the 4004 itself and its potential applications beyond its first intended use? Can’t see how that makes sense at all.

Your statement about Intel 'pushing back' the date to 1971 also makes little sense given Intel advertised [1] the 4004 as a CPU in Electronic News in Nov 1971.

[1] https://en.wikipedia.org/wiki/Intel_4004#/media/File:Intel_4...

Because of its purpose, Intel 4004 did not have many features that had been recognized as necessary already since the first automatic computers, for example the lack of logic operations, which was mentioned in the parent article.

Therefore I do not believe that it is possible to consider Intel 4004 as a general-purpose processor. It had only the features strictly necessary for the implementation of the Busicom calculator.

The idea to sell 4004 for other uses has appeared long after the design was finished, when Busicom did not want to pay for the chipset as much as Intel desired, so Intel decided to try to sell the chipset to other customers too, and then they thought to advertise it as a "CPU".

Moreover, it is debatable whether Intel 4004 can be considered as a monolithic processor, because 4004 was not really usable without the rest of the chipset, which provided some of the functions that are normally considered to belong into a processor.

The Intel 4004 4-bit "CPU" implemented less functions than the 4-bit TTL ALU 74181, which was general-purpose and which was the main alternative at that time for implementing a CPU, but it had the advantage of including many registers, because the MOS registers were much cheaper in die area than the TTL registers, and these included registers were the reason why a CPU implemented with the Intel 4004 chipset had a lower integrated circuit count than the equivalent implementation with MSI TTL ICs.

Intel's advertisement of 4004 being a CPU was just an advertisement of the same kind of Tesla having a "Full Self-Driving".

> Because of its purpose, Intel 4004 did not have many features that had been recognized as necessary already since the first automatic computers, for example the lack of logic operations, which was mentioned in the parent article.

So you're setting a range of instructions without which a device can't be considered a general-purpose computer even if the missing instructions can be recreated in software with instructions that do exist.

Sorry disagree with this completely, as does every definition I've ever seen.

No, logic operations aren't "recognized as necessary". For instance, the IBM 1401—the most popular computer of the early 1960s—did not have logic operations. (This was very annoying when I implemented Bitcoin mining on it.)

The reason that the 4004 is considered a CPU and the 74181 is not a CPU is that the 4004 contains the control logic, while the 74181 is only the ALU.

Of course, "microprocessor" and "CPU" are social constructs, not objective definitions. (For instance, bit-slice processors like the Am2901 were considered microprocessors in Russia.) So you can craft your own definition if you want to declare a particular processor first. cough MP944 cough

No kidding about unusual uses of ICs. Not related to microprocessors, but I have an old analog triple conversion HF receiver (Eddystone EC958/3 for what it's worth) that uses a TTL IC in an analog circuit! I'd have to look at the schematic again, I think it's a multi-stage counter, but basically what it uses it for is to generate a comb shaped spectrum, one "spike" of which can then be picked up by an analog circuit and locked to, to generate precisely spaced tuning steps for the high stability tuning.

The naming and propaganda wouldn’t matter. I just wanted something lower-end for sure than a 6510 and an AVR. 4004 is that

Is this the oldest piece of hardware that's ever run Linux, I'm left wondering?

It surely is

I'd figure the earliest thing anybody has run Linux on before this would be a 386. Although I suppose with this MIPS emulator ported to some other proto-processors it could go older, but just getting the hardware to do that would be a challenge.

PS: love the VFD

There was a 286 Xenix, and Minix (which inspired Linux) ran on an 8088.

Yeah, and UNIX was developed on a PDP-7 as far back as 1969. But I was talking about Linux.

Linux will run on a 68020 which is a couple of years older than a 386.

Glad to see someone besides me posting this whenever 4004 history-rewriting comes up.

IMO, just because a microprocessor has a quirky instruction set that doesn't include some standard instructions, or was made for a specific purpose in mind, doesn't make it not a microprocessor.

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