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To qualify what I mean by "16-bit microcomputer system", I am talking about a system that has not only a 16-bit (or 32-bit) microprocessor CPU, but also a 16-bit wide external data bus connected to the rest of the system. So, 16-bit access to its primary RAM, and the possibility of 16-bit wide access to peripherals.

To qualify as "mass-market", the system should have been generally available for purchase by consumers in quantity as a general-purpose, desktop style, computer in the vein that became popularized as "personal computers". So, no prototypes, experimental, kit, or bespoke systems. Basically a conventional microcomputer marketed to business, professional, and/or home computer users.

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    By your comments about the 16-bit wide external data bus, are you saying that to specifically exclude the IBM PC which had a logical 16-bit bus but was actually 8-bit in hardware? Mar 26 '17 at 23:12
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    @GregHewgill The 68000 is classed as a 16 bit CPU. It's data bus both internal and external was 16 bits.
    – JeremyP
    Mar 27 '17 at 9:11
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    @JeremyP quite a few people prefer the size-of-the-main-registers test, as if it were about the external data bus then the Pentium is 64 bit. If it were about the internal data bus then the Z80 could be 4 bit. So instruction set architecture is the thing. Though clearly it wasn't at the time because, well, what does the writing on the front of a Mega Drive say?
    – Tommy
    Mar 27 '17 at 12:14
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    How do you want systems with WIDER than 16 bit (and non-multiple-of-16) bus widths treated? And BTW; both the AT and some early Macintosh were more or less 24 bit systems in hardware :) Apr 27 '17 at 21:59
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    When used without any expansion, the directly-accessible memory in the TI/994a consists of a pair of 128x8 static RAM chips and 4Kx8 ROM chips, all sitting on a 16-bit-wide bus. Although the video subsystem includes eight 16Kx1 DRAM chips, the CPU can't randomly access the contents thereof directly but must instead use a sequence of store operations to tell the video chip what part of the video chip's storage the CPU would like to read or write, and then read or write bytes sequentially from there.
    – supercat
    Oct 3 '20 at 16:32
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A number of mass-market microcomputers which could be qualified as home computers were released in 1982 or 1983, earlier than the Electronika BK:

  • the Olivetti M20 was a 16-bit computer based on the Z8001 with a 16-bit data bus (March 1982);
  • the Olivetti M24 was the first fully-compatible IBM PC clone, and it used a fully 16-bit 8086 and a 16-bit peripheral bus; it was quite popular in Europe (introduced sometime in 1983);
  • the Apple Lisa, while a commercial failure in the end, was widely available and used a 16-bit bus (introduced on January 19, 1983);
  • in Japan, the NEC PC-9801 also used the 8086 and had a 16-bit bus (the C-bus); it started the PC-98 line which would dominate the Japanese market well into the nineties (introduced in October 1982).

Looking into early 16-bit microprocessors leads to a number of earlier microcomputers that aren’t as famous as the above:

  • the Western Digital WD-9000, which implemented p-code in its microcode (1979, although it wasn’t debugged and widely available before 1981);
  • the Alpha Microsystems AM-100, based on the same Western Digital chipset (the technical manual is stamped January 13, 1979);
  • the NEC N5200, with a similar architecture to the PC-9801 but released earlier (available in December 1981).

In the microcomputer-sized mini category, the IBM 5100 was a 16-bit portable computer released in September 1975; the earlier-still HP 9830A, released in 1972, was marketed as a calculator but had BASIC in ROM and was effectively a desktop computer (and used as such).

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    I was looking for mass-market models which might be earlier than those @scruss mentions, not necessarily going for a survey (although I could write that up...). The Lisa isn't really mass-market IMO, with only 100,000 sold (v. at least a million M24s and even more PC-9801s). Mar 27 '17 at 11:38
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    The Model 16 had an 8-bit I/O bus, so no 16-bit-wide access to peripherals. Mar 28 '17 at 4:28
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    The Zilog System 8000 "supermicro" (really more of a mini, given its size) from 1981 used the Z8001. But early 1980s Olivetti kit was very far ahead of its time.
    – scruss
    Mar 28 '17 at 18:09
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    @mnem according to the service manual, memory is accessed directly by the 68k, with up to 16 data lines (there’s also a nifty MMU with kernel/user distinctions, providing inter-process protection); but only the interrupt controller and the MMU are reachable from the 68k, all other I/O goes through the Z80 and its 8-bit bus. Apr 27 '17 at 20:41
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    @njuffa the TI-99/4A has been addressed in other comments — it had a 16-bit CPU, but only its ROM and 256 bytes of RAM were available on the 16-bit bus, everything else went through an 8-bit multiplexer. Apr 28 '17 at 7:37
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The Heathkit H11 was available fully assembled and tested for $1595 in 1978. It was a clone of the PDP-11 minicomputer in a desktop case.

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    This is clearly the winner of the "contest". It was available to anyone with a Heathkit catalog and ran in a stand-alone fashion. Jun 17 '18 at 12:01
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    Also, I don't think it was a clone, was it? Didn't it use an actual DEC LSI-11 CPU?
    – cjs
    Sep 19 '19 at 20:47
  • You needed a separate terminal and external storage. In 1978, these two requirements would stop it from being a desktop system.
    – JeremyP
    Nov 3 at 16:16
  • @JeremyP If the keyboard, monitor, and non-volatile storage weren't integrated into the chassis, it wasn't a desktop computer? Nov 3 at 19:46
  • @snips-n-snails If you can't put it on the top of the desk, it's not a desktop computer. You're talking about a terminal that would be significantly bigger than a modern PC thanks to needing a CRT display, the computer itself, probably packaged for a 19 inch rack and a disk drive. Here's a DEC RP06 from 1977. It's about the size and shape of a top loading washing machine.
    – JeremyP
    Nov 4 at 8:56
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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Chenmunka
    Oct 4 '20 at 10:18
7

In 1979 or 1980, Convergent Technologies released their IWS (Integrated WorkStation). This was based on the Intel iapx86 (8086), and came in two configurations - the older configuration had the CPU and disk drives in separate "towers" somewhat larger than a current PC, with a CRT on the desk; the second configuration moved the CPU to a box approximately the size of a modern "pizza box" (but about twice as thick in the smallest dimension) CPU attached to a base, with a CRT attached to its left to the same base. The disk drives were 8", both floppy and hard.

In 1980 or 1981, the next generation of Convergent Technologies workstations were released, the AWS (Advanced WorkStation). This had essentially identical capabilities to the IWS, but the disk drives were incorporated into the the on-desk CPU configuration, and it used 5.25" ("full-height") drives rather than 8".

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  • Interesting. Sparse info on the web for Convergent. Do you have any good links that might better pinpoint a release date for a product they sold in significant quantity?
    – Brian H
    Mar 27 '17 at 13:12
  • I'm afraid not. Convergent sold very little under their own brand; most of their sales were to other companies that rebranded them. Some names to look for would be the Burroughs B21 and B22 (the B25 was also a (later) Convergent design), the NCR WorkSaver, the Mohawk Data Sciences HERO (later Momentum HERO), and the Prime Producer. The original of the B25 was also sold by DataPoint as the Vista PC, but I don't know if DataPoint also sold the AWS and IWS. The second-design IWS or AWS (can't tell which) is pictured here. Mar 27 '17 at 13:30
  • There's a lot of info on bitsavers, including brochures, but I'm not sure there's anything that would give release dates for products with significant sales. Mar 27 '17 at 13:31
  • Addendum to my previous comment: I took a closer look at the pictures from the link (one of which could be zoomed), and it reveals that there are no disk drives in the CPU box on the right. That makes it a second-design IWS, rather than an AWS. May 2 '17 at 7:41
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How about the LSI-11/2 (PDP-11/03) that was released in 1975? These machines were in small cabinets you could put beside your desk (not the 6' tall H960 rack). And they were used in process control, science and other fields. It was also available OEM for inclusion into other equipment.

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