When IBM developed the PC, they famously chose a bunch of off-the-shelf components. Besides making the machine relatively easy to clone, another effect of this was it used a lot of chips and board space. Consider that a usable IBM PC system with peripherals needed 3 to 4 expansion cards for:

  • Video adapter
  • Floppy and/or HD controller
  • Serial and Parallel ports

Effectively doubling the amount of board space over and above the already large slotted motherboard.

My question is what was the first 100% PC compatible with these basic I/O features built-in on the motherboard? Also, how did they "fit it all" given the legacy of off-the-shelf only components?

NOTE: If the answer is a PC with no ISA slots, then I'd also like to know which was the first that also retained expandability by including some slots.

NOTE 2 (Trying to define "100% compatibility" more pedantically): To my mind, 100% compatibility just means "all the same software media". So the strict requirement is really binary compatibility, and even software that bypasses BIOS and bangs the hardware directly, still works as expected. The secondary requirement would be ISA slots, if it has slots at all, to facilitate off-the-shelf hardware from the general PC expansion card market. So, yeah, you can buy software and hardware for the PC and it works just fine with your 100% compatible clone... This was the standard consumer's aspiration at the time, I think.

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    To discount the obvious guess: even the early Compaqs have expansion cards, including the CGA, installed inside the case rather than directly integrated onto the board: old-computers.com/museum/photos.asp?t=1&c=870&st=1 and see inside #2.
    – Tommy
    Commented Jul 3, 2018 at 2:06
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    I remember when the Mac II came out, what a sparse board it had. CPU and a couple of ASICs, and misc. discrete components compared to most every PC board I saw at the time. Commented Jul 3, 2018 at 4:38
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    It's not 100% PC compatible (though it could run MS-DOS) but the PC-9801F released in 1983 had video, floppy, serial and printer ports on the motherboard.
    – user722
    Commented Jul 3, 2018 at 6:06
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    For proof of @Raffzahn’s last point, try running 8088MPH on any IBM PC other than the original ;-). Commented Jul 3, 2018 at 15:44
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    @BrianH I’m not saying it has strict requirements for its execution, just to reproduce the result intended by its authors (the two main constraints being the two you mention: CGA composite and the exact speed of the 4.77 MHz 8088). Commented Jul 3, 2018 at 21:09

3 Answers 3


A candidate for the first integrated PC-compatible with expansion slots is the Amstrad PC1512, released in 1986. Its original configuration, with only floppy drives, didn’t use any expansion card; models with hard drives had a controller card (in fact the drive itself was usually mounted on the card). It had a number of custom chips (Amstrad were used to making their own chips, as demonstrated with the CPC range).

Amstrad continued this trend in later models (PC1640, PPC512, PC20, PC2086 etc.).

  • I tend to agree, except the PC1512 wasn't 100% compatible. Different CPU (8086), incompatible mouse interface, some differences in BIOS handling (i.e. clock) and while it was basicly an integrated EGA, not all CGA modes where supported or supported the same way IBM did.
    – Raffzahn
    Commented Jul 3, 2018 at 11:02
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    @Raffzahn: The PC1512 video hardware is CGA with an extra 4-plane graphics mode, nothing like EGA. I'd also find it hard to complain about the mouse interface since no IBM PC had an integrated mouse interface in 1986, and there was nothing to stop the user connecting a bus mouse or serial mouse to the PC1512 exactly as they would for an IBM.
    – john_e
    Commented Jul 3, 2018 at 14:33
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    There's a big chip in the middle of the PC1512 motherboard labeled "Amstrad", suggesting some real re-implementation and integration of the PC circuitry to "fit it all". I don't know much about the Amstrad PC line's reputation for compatibility. Was it as good as Tandy's reputation in N. America? Could it be underclocked to 4.77MHz like the Tandy?
    – Brian H
    Commented Jul 3, 2018 at 15:12
  • @Brian Amstrad PCs had a good reputation for compatibility. I think the only major shortcomings of the PC1512 are that the 6845 is emulated and doesn’t support all the real 6845 registers, that its CGA implementation is awfully slow, and that its CPU speed apparently isn’t changeable (at least, Nerdly Pleasures claims it isn’t; I can’t really remember, all I know is that the later PC20 did have a user-selectable clock speed for backwards compatibility). Later Amstrad PCs were better. Commented Jul 3, 2018 at 21:18
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    @Brian that’s a good question, and there are two relevant changes: IDE (1986) which moved most of the electronics onto the drives, removing the need for complex controllers (which typically weren’t integrated), and VGA (1987), which was designed as an ASIC merging a number of discrete chips, making it easy to integrate. Commented Jul 4, 2018 at 5:22

My question is what was the first 100% PC compatible with these basic I/O features built-in on the motherboard?

This question is a bit tricky, as it adds several constrains. For example requesting a parallel port isn't all that logical, as back in the early 1980s the race for the 'right' printer interface wasn't as decided as 10 years later. But let's see the candidates.

  • Sanyo MBC-550 of spring 1982 - calling it compatible might be borderline. It did feature parallel port, floppy controller and graphics direct on board, with the graphics partial CGA compatible. It did not feature an ISA bus, but a custom pin header for up to two stacked I/O (one offer was a true CGA compatible board). Missing an on board BIOS, software compatibility due the disk loaded BIOS was poor at first, but improved quite a lot later on. Another hurdle for full compatibility would be the slower CPU speed of 3.58 MHz.

  • Columbia Data Products MPC-1600 of June 1982 - while being a true compatible and including parallel and serial interfaces and floppy controller on board, CRT was still handled via a standard ISA card.

  • Columbia Data Products MPC-VP in 1983 followed the same scheme, just this time portable.

  • Olivetti M24 in 1983 - while highly compatible, it wasn't a 100% at least due it's 7 MHz 8086. Also the design wasn't a single PCB but kind of a stacked one with the main board on the bottom, the I/O board on top, both connected via the video board angled at 90 degrees. While it's not a single PCB, they are no separate available add-on cards either.

  • Compaq Portable in March 1983 - a true compatible despite a somewhat different graphics 'card' design combining features of CGA and MDA. Notably the first with a BIOS as compatible as possible. The Compaq Deskpro moved that concept to the desktop.

  • IBM PCjr in March 1983 - while integrating many features like joystick ports, sound and a serial port, the floppy controller was still on a separate board - one of the bad design decision around the Peanut - even though not necessarily the reason for its failure.

  • And then there is the Tandy 1000 series which offered all in one machines in many configurations, starting in late 1984.

Before deciding, honourable mentions, due being less than compatible, should got to

  • Sirius 1 of 1981 - at the same time as the PC this machine already included a faster CPU, more RAM, HD Audio, 800x400 graphics and 1.2 MB disk drives.

  • DEC Rainbow 100 of 1982 - as an example for ambition and failure of a large player

  • Apricot PC of 1983 - maybe the slickest of all (early) PC-alikes. Especially with the later F1 and Portable (*1,2)

  • Amstrad PC1512 of 1986, Olivetti Prodest PC1 of 1988 and Schneider EuroPC of 1988 as examples of later consumer/home computer orientated all in one PC-alikes

So, who was the first to fit all these criteria?

Hard to tell. Personally I'd vote for the CDP MPC-1600 by fulfilling the 100% criteria and integrating everything except the video card, which does make sense. Going by the wording it must be the Compaq Portable

Also, how did they "fit it all" given the legacy of off-the-shelf only components?

That wasn't a big deal, considering that the original PC was neither high integrated nor really dense packed. Much of the circuitry could have already back then improved by PALs and GALs without increasing the cost. The Sirius 1, debut the same time as the PC, is a prime example what was possible.

*1 - Most notably here the usage of an 8089 IO-processor.

*2 - To some degree the later Acorn Archimedes continued that design.

  • The Tandy 1000 all-in-one computers didn't arrive until 1986 (EX) and 1987 (HX). Commented Jul 3, 2018 at 14:09
  • The Compaq Portable was effectively a Deskpro with a screen inside the case, and used expansion cards; it had five expansion slots, two of which were taken. Its notable integration effort (at the time) was to merge the parallel card and FDC. Following your criteria for other systems, the Compaq isn’t “100% compatible” either since its graphics controller is a combined CGA/MDA controller. Commented Jul 3, 2018 at 14:42
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    @traal I refered xplicit to the whole series. But already the first Tandy 1000 was an all in one board featuring graphics, serial port and floppy (plus other) interface on board - ancientelectronics.wordpress.com/2012/11/27/…
    – Raffzahn
    Commented Jul 3, 2018 at 15:12
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    @traal: I had a Tandy 1000 before the EX/HX came out, and I think it met your qualifications except for the serial port. Given that the only thing most people would have used serial ports for would have been a modem, and internal modems were cheaper than external modems, I'm not sure a serial port would have been seen as useful. One slight nit with the Tandy 1000 which I've not seen mentioned much: modems that require a -5V rail won't work with the T1000 unless one uses an extender card with a 7905 regulator added on to it (ask how I know this).
    – supercat
    Commented Jul 3, 2018 at 15:39
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    @Raffzahn... One example of the Compaq video adapter's compatibility problems with respect to CGA relates to the fact that it was incompatible with overhead projector LCD's that depended on 200 line resolution, unless specific steps were taken. (I found this out the hard way, trying to give a demo to a class.)
    – mschaef
    Commented Jul 5, 2018 at 22:51

My guess is the Toshiba T1100, released in April 1985. (Another link.) The system board contains the CPU, memory, graphics controller, floppy controller, and printer port. Memory expansion and serial I/O cards were optional. It ran MS-DOS and is "Compatible with most software written for the IBM PC/XT using a color graphics adapter (CGA) display." However, the T1100 requires its own custom version of MS-DOS. (See the manual.)

  • While beeing a good bet, it doesn't fit the 100% compatible requirement, does it?
    – Raffzahn
    Commented Jul 3, 2018 at 11:06
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    It's a tough requirement. For example there are video modes that are only available on the original CGA card, not on later EGA or VGA cards. Also timing differences make a lot of games run too fast on faster CPUs. Commented Jul 3, 2018 at 14:15
  • Admittedly the T1100 requires its own custom version of MS-DOS. I will add this to my answer. Commented Jul 3, 2018 at 14:23
  • Needing a proprietary version even for DOS doesn't paint a good image for compatibility. I know Tandy 1000s had their own DOS too, but were well-known for being highly compatible. In the Tandy case, you were able to load up off-the-shelf MS-DOS if you wanted.
    – Brian H
    Commented Jul 3, 2018 at 14:57
  • @BrianH: I think the Tandy used their own DOS for licensing systems. A Tandy could boot from a generic MS-DOS disk just fine, but Tandy would likely have had to pay more to bundle MS-DOS boot disks that could boot anywhere, than to bundle disks that were only usable with Tandy computers.
    – supercat
    Commented Jul 3, 2018 at 15:33

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