
The Story of the First Microprocessors - jonbaer
http://spectrum.ieee.org/computing/hardware/the-surprising-story-of-the-first-microprocessors
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boyaka
Masatoshi Shima deserves more credit than anybody. He was responsible for most
of the logic in the 4004 and the 8080. Should write an article that summarizes
what goes on in these oral history discussions:

4004:
[http://archive.computerhistory.org/resources/access/text/201...](http://archive.computerhistory.org/resources/access/text/2012/08/102657974-05-01-acc.pdf)

8080:
[http://archive.computerhistory.org/resources/access/text/201...](http://archive.computerhistory.org/resources/access/text/2012/08/102657974-05-01-acc.pdf)

z80:
[http://archive.computerhistory.org/resources/text/Oral_Histo...](http://archive.computerhistory.org/resources/text/Oral_History/Zilog_Z80/102658073.05.01.pdf)

~~~
boyaka
Pasted the wrong link for 8080:
[http://archive.computerhistory.org/resources/access/text/201...](http://archive.computerhistory.org/resources/access/text/2013/05/102658123-05-01-acc.pdf)

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tostitos1979
Here is a factoid for the youngins ... the Internet/Arpanet was created BEFORE
the first microprocessor! In fact, Intel was originally founded to make RAM
ICs. They only later created the first microprocessor (the 4004)!

~~~
DigitalJack
Back then, it really was a bunch tubes.

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mzs
Here's a PDF describing the system that Lee Boysel demoed during the TI case:

[http://corphist.computerhistory.org/corphist/documents/doc-4...](http://corphist.computerhistory.org/corphist/documents/doc-4946dbc7a541f.pdf)

~~~
kens
Boysel's demo is an amazing hack, but in no way is the AL1 chip a
microprocessor. The demo seems convincing - he hooked up an AL1 "CPU" with
RAM, ROM and I/O and ran programs on it. But I looked in detail and there are
some problems.

The AL1 chip is an 8-bit arithmetic/logic chip with some registers. It does no
instruction fetching, no instruction decoding, and doesn't have an instruction
set. It doesn't implement any control functions. It doesn't perform memory or
I/O operations. (It's similar to a 74181 ALU chip with registers.) So how can
it operate as a CPU?

The trick in the demo is the ROM has a "ROM memory address registers", which
seems like an innocent latch. But this latch is under the control of the ROM,
not the "CPU". The ROM and latch form a state machine that is controlling the
system, performing RAM and I/O operations and directing the AL1 chip to
perform ALU operations. The ROM is not sending instructions to the "CPU"; the
ROM is running the show. The ROM doesn't hold AL1 instructions; it holds crazy
microcode-like sequences that get the system to stumble through operations.
There's no program counter as such, just the ROM jumping from address to
address.

In other words, if you think of a microprocessor as ALU + control, the AL1
chip has only the ALU half, not the control half. The ROM-based state machine
provides the control half.

I'll also point out that the AL1 die photo [1] from the demo is kind of bogus.
Near the bottom is the label "instruction register 23 bits" \- the chip has no
instruction register and the label is dropped on top of some clock lines.
Saying the chip has an instruction register makes it sound much more like a
CPU, but it's just fiction.

To conclude, I am extremely impressed that Boysel was able to get the demo
working. But don't be tricked into thinking the AL1 is a microprocessor.

[1] [http://www.computerhistory.org/revolution/digital-
logic/12/2...](http://www.computerhistory.org/revolution/digital-
logic/12/282/1523)

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jloughry
Aha! Thank you for the explanation. It works a bit like the Apple II disk
controller, then.

~~~
kens
Ha! That's not an analogy I would have thought of, but yes, it's the same ROM
+ latch state machine architecture as the Apple II disk controller. The demo's
state machine generated a lot more control signals (24) and controlled the
RAM, I/O and the ALU chip rather than a disk drive, but the concept is very
similar.

(Background: Wozniak's design for the Apple II disk controller used very few
chips. A ROM and latch implemented a simple state machine that did much of the
control sequencing. The CPU also did a lot of the low-level control.)

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davidw
Federico Faggin went to the University of Padova. I guess that's not of
interest to most people, but having spent much of the past 15 years there, I
always thought it was kind of cool.

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gens
The transistor was invented in 1925 by Julius Edgar Lilienfeld (a FET). The
first one built was in 1947 (a BJT).

A metal-oxide (MOS) transistor is a FET. Commonly known as MOSFET.

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anonymous_iwas
No mention of Mostek, RCA, Rockwell, Motorola, or Signetics.

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monocasa
They do mention MOSTEK in passing, but this article is literally about who
created the first single chip microprocessor. Those other companies aren't
even in the running.

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dboreham
At least Pico/GI got a mention. I grew up in that area during this period, and
my Dad knew a few of the engineers through his work. Also I rode the train to
school with a girl around my age who I (much) later discovered was the
daughter of the lead designer for their CPU. If only I had known how cool she
was ;)

[https://en.wikipedia.org/wiki/Microprocessor#Pico.2FGeneral_...](https://en.wikipedia.org/wiki/Microprocessor#Pico.2FGeneral_Instrument)

[http://www.spingal.plus.com/micro/](http://www.spingal.plus.com/micro/)

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anonymous_iwas
Or Zilog.

~~~
dboreham
Zilog the company wasn't founded until 1974, years after the first
microprocessors were made.

