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It seems that integrated circuits of the 1970s tended to have 4-digit part numbers. This includes not only the ones that came to be well-known like CPUs (Intel 4004, 8008, 8080, 8085, 8086, 8088, Motorola 6800, 6809, MOS Technology 6502, 6507), but also the 7400 series, memory chips like the Intel 1103 and Mostek 4096, graphics chips like the MOS Technology 6567/8562/8564/6569/8565/8566, better known as the VIC-II, still better known as the graphics chip developed for the Commodore 64, etc.

It looks like there was a global namespace of 4-digit numbers that all the companies used. (Indeed it was common for a particular chip to be manufactured by multiple companies; big customers often insisted on second sources.) But I haven't seen any mention of a registry of numbers used, or any other central way of avoiding collisions.

How did they avoid collisions? Was there even any such thing as a comprehensive catalog of chips listed by number, that you could look up to make sure a candidate number wasn't already in use?

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    However the company assigning the numbers wanted to. Presumably they would want to avoid confusion with the same numbers being used for different products, but there was no requirement that they do so.
    – user722
    Nov 21 '20 at 20:47
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    TL;DR: "Arbitrarily" :)
    – Kuba hasn't forgotten Monica
    Nov 23 '20 at 0:21
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    When Motorola wanted to copy RCA's CD4000 CMOS logic they had a problem - they already had some 4000 series parts, so they added a "1" prefix to their CMOS logic parts - a CD4000 became an MC14000.
    – Peter Bennett
    Nov 23 '20 at 2:26
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    Interestingly, unlike American ICs, Soviet integrated circuits used a structured system for part numbers. For instance, a half adder part number would contain ИЛ while a NAND gate would have ЛА. en.wikipedia.org/wiki/Soviet_integrated_circuit_designation
    – Ken Shirriff
    Mar 7 at 18:33
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It seems that integrated circuits of the 1970s tended to have 4-digit part numbers.

Not really. Anything from letters to numbers and 3 to 7 characters have been used. even with numbers like 7400, the chips name wasn't just the number, but a letter number combination, like SN7400.

Other than often assumed is SN not a prefix used to indicate TI, but the 'family' TI puts that chip into. 'Family' in quotes as it's not really a technological differentiation but rather organisational - exactly to avoid collisions if different divisions use the same number. In addition some of the prefixes are historical. Examples for prefixes used by TI are:

  • CA - Analogue, inherited from RCA
  • CD - Digital, inherited from RCA
  • SN - 'regular' digital
  • RSN - Radiation hardened digital
  • SNJ - Mil Spec Digital
  • TL - Linear
  • TMS - Data Processing (computer)

There're might be more - we in digital electronics are simply way too used to 'SN', not seeing the rest.

Other companies made up similar distinction (Like Altera with EP/EPC/EPF), while on the other end small newcommers wanted to fit in and simply added their company mark in front, like CY for Cypress or MAX for Maxim. Important is, that all of these letters are integral part of the 'name', not just ignorable prefixes.

In addition people often add a manufacturers abbreviation to the name when needed, like TI-SN7400.

It looks like there was a global namespace of 4-digit numbers that all the companies used.

No, there wasn't. Every manufacturer used it's own system. Well, except there was an attempt to standardize names on functionality in Europe. It did make inroad for diodes and some analogue IC, but never cought on for digital/TTL.

Indeed it was common for a particular chip to be manufactured by multiple companies

Sure, if one wants to sell a compatible chip, he named it alike to pave the way for customers to find and buy his chips. Although, it did need a learning curve from marketing. Especially visible with early RAM (*1) and ROM chips, were functional identical chips had different names, leading to long lists of equivalent models.

Heck, even companies that licenced other companies designs re-'named' them. A good example would be AMD's AM9511 FPU of 1979(?), licenced and marketed by Intel as C8231.

This changed a bit when chip names, especially the numeric part, became household names if not brands (but really only a bit).

But I haven't seen any mention of a registry of numbers used, or any other central way of avoiding collisions.

Corse there was none.

How did they avoid collisions?

They simply didn't.

Was there even any such thing as a comprehensive catalogue of chips listed by number, that you could look up to make sure a candidate number wasn't already in use?

Well, there were huge IC databooks, sold for unimaginary high prices by third party publisher - 1000 USD for a comprehensive list wasn't out of the ordinary (and we're talking 1980s USD). But their use wasn't about avoiding collisions, but helping engineers finding the chips they need, or equivalent chips from other manufacturers - like when looking for a replacement or lower prices.

It was as well the high time of chip brokers, firms specialized in keeping an overview, consulting and often arranging a deal/sales.

*1 - For example chips compatible (or licenced) with the well known Mostek MK4116 16 KiBit RAM were available as (peeked from an old paper under my desk mat):

  • AM9016 from AMD
  • F16K from Fairchild
  • MB8116/MB8216 from Fujitsu
  • HM4716 from Hitachi
  • 2117 from Intel
  • M58759 from Mitsubishi
  • MM5290 from National
  • uPD416 from NEC
  • MSM3716 from OKI
  • LH6116 from Sharp
  • N2690 from Signetics

Not to mention that Mostek as well sold them as MKB4116 in military grade and MKI in industrial grade :)

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    Do you know if TMS is an initialism? It was used for the TMS1000 microcontroller, which used mask-programmed ROM. Later it was used for the TMS9900 microprocessor.
    – Single Malt
    Nov 22 '20 at 10:57
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    Also it was extremely common for an equipment vendor who sourced their chips from multiple sources to overprint them with their own designation... which might be distinct from their company-wide parts catalogues. So Burroughs- as an example- bought CTL latches from Fairchild and marked them up as RFAN... until they were found to be a defective design and their replacement was labelled RFZN. The alert reader will have noticed that those 4-character codes weren't numeric...
    – Mark Morgan Lloyd
    Nov 22 '20 at 12:58
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    @MarkMorganLloyd, a big enough company would simply order the parts specially marked with their house numbers (instead of the manufacturer's usual designations) from the chip maker. I've worked at HP spin-offs where we still had drawers of old parts marked with HP "4+4" numbers (like 9876-1234) instead of the more usual numbers (like 7404).
    – The Photon
    Nov 23 '20 at 18:39
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    @ThePhoton Compared with Burroughs in its heyday HP was a fiddling little post-war upstart. However their fortunes diverged drastically in the late 60s and 70s: by the time I worked for them Burroughs was but a shadow of its former self.
    – Mark Morgan Lloyd
    Nov 23 '20 at 21:23
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    @MaxW True. Manufacturer databooks were usually rather affordable. But original manufacturers rarely added lists of compatible chips, while manufacturers of compatible chips more often than not only tables assigning their numbers to the original part umbers, not offering hints about their competition. Only third party books (like IC-Master) offered comprehensive equivalence tables - and let users pay for that knowledge.
    – Raffzahn
    Nov 25 '20 at 20:13
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I guess the first one (Texas Instruments in the case of TTL) settled some number prefixes (74xx, 54xx) and start its own series, which became de facto standard. Other manufacturers later adopt the same numbering (with a different alphabet prefix than "SN") for the same ICs. There were minor collisions, but the bigger manufacturer just pushed the others out of their "number tracks".

But in the rare cases of collisions, there were relatively harmless, because the ICs were not only part number but the manufacturer letter prefix (or postfix) too. SN is used by Texas Instruments for TTL (TI uses other denominators too, like CD for CMOS), MC by (former) Motorola, etc.

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    While it may seam like, SN does not denote TI, but the chip type. TI uses for examle as well CA for analogue circuits, CD for CMOS and RSN for radiation hardened variants of SN, SNJ for the same in MIL, TL for linear and so on...
    – Raffzahn
    Nov 21 '20 at 21:05
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    Sorry for my poor English. I mean "SN is used by TI", not "SN means TI". I'll clarify it.
    – Martin Maly
    Nov 22 '20 at 10:37
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    @Raffzahn: I believe SN is a TI prefix - other makers used different prefixes for equivalent parts - National used DM for their TTL and other digital parts, if I recall correctly.
    – Peter Bennett
    Nov 23 '20 at 2:15
  • @PeterBennett Of course is SN a prefix used by TI, but it does not mean TI. Please read here for more details
    – Raffzahn
    Nov 23 '20 at 3:09

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