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IBM PC DOS 2000: An underrated DOS

What’s the ideal operating system to run on a retro PC? There are several names you hear over and over again. MS-DOS 6.22 is probably the most frequent option. MS-DOS 3.31 is one that comes up from time to time. I don’t think enough people talk about IBM PC DOS 2000. I think it’s an underrated choice.

IBM PC DOS 2000 was derived from the same code base as MS DOS 6.22, so it has a very high degree of compatibility with the most popular retro DOS. But it also has some advantages.

IBM and Microsoft


If you need a DOS for your retro PC, IBM PC DOS 2000 is an underrated choice. Think of it like an MS-DOS 6.22 with a lower memory footprint.

Microsoft and IBM had a complicated relationship throughout the 1980s and 1990s. They started out the decade as partners, and IBM frequently sought Microsoft’s advice as they designed the IBM PC and brought it to market.

We will probably never know to what extent IBM understood the implications of the deal they made with Microsoft. The important thing to know is that Microsoft did not sell DOS to IBM. They licensed it to IBM, and crucially, they didn’t give IBM an exclusive license. That whole relationship is another story. But until sometime around 1991, IBM was completely uninterested in selling DOS for use on anything but a genuine IBM PC. Even then, it was an afterthought. The IBM PC DOS 5.0 box states “For IBM and IBM compatible PCs.”

Curiously, the PC DOS 2000 retail box doesn’t state that. It might have been worth mentioning.

Selling PC DOS for non IBM PCs

With version 6, IBM decided to try competing directly with Microsoft, selling IBM PC DOS at retail, promoting it and advertising it. I worked at retail during this time frame, and the IBM sales reps likes me, because we could tell I wasn’t a Microsoft fanboy. I asked them what made PC DOS different, and they told me it was the same code base but IBM found and fixed some minor bugs and used their own compiler instead of Microsoft’s compiler, and the result was about 10% faster and it used a bit less memory.

They also emphasized it ran just fine on other brands of PCs.

I gave it a whirl on my Compaq. And I didn’t have any problems. I’m not sure I noticed any significant improvement either, but it didn’t give me problems. I did notice that OS/2 version 3 ran DOS programs faster than either IBM PC DOS or MS DOS did.

IBM ended up selling four iterations of PC DOS at retail: version 6.1, 6.3, 7.0, and 2000.

There is less difference between any of them than there was between them and DOS 5. All of them were slightly souped up versions of the MS DOS 6 code base.

What’s special about DOS 2000

IBM PC DOS 2000 is basically MS-DOS 6.22 with Y2K bug fixes and memory optimizations. It has the same overall memory layout as Microsoft’s version, it uses the same command syntax and structure for boot menus, but it is also tuned to be a bit more efficient in its conventional memory usage, and in how much of the operating system it can load into upper memory or the high memory area.

The result is that when you run PC DOS 2000 on a 386 or faster PC, you get a bit more conventional memory available.

And even when you run it on a 286 or XT, it uses less conventional memory then any version of DOS prior to version 3.31. So you can run it on PCs that conventional wisdom say there’s no point in upgrading past version 3.31. The benefit is you get boot menus, a nicer text editor, command history, and the ability to use large disk partitions.

What you don’t got are certain utilities that Microsoft included in MS-DOS. You don’t get Microsoft’s editor and you don’t get memmaker or Microsoft’s disk compression, notably. If you want a 6.22 like experience, you can install 6.22, and then upgrade to PC DOS 2000. Then you will have the Microsoft utilities, and they run fine under PC DOS, along with the efficiencies of PC DOS 2000.

Why didn’t everyone buy it at the time?

In my experience, consumers were curious about IBM DOS during the DOS 6 era, but skeptical. IBM priced it aggressively, undercutting Microsoft by about 10%, which was enough to encourage people to ask questions.

The conversation always went along these lines: vast what the difference was. I told them they were compatible but the IBM product was a little bit cheaper and slightly better. They asked how it was better, and I said it was a little bit faster and more efficient and it was completely compatible as far as anyone new. Then they pointed at novel DOS sitting next to the two, which was priced the same as MS DOS, and they asked about that. I said it was a great product, had similar benefits to IBM DOS, but I was aware of some compatibility problems. And as far as anyone knew, there were no known compatibility problems between the IBM and Microsoft products.

But the conversation almost always ended with the customer hemming and hawing a bit, saying they didn’t see the point of switching to IBM, and picking up the Microsoft box.

I remember one of them phrasing it like a question and looking at me like they expected me to respond. And I said the reason to switch was because it was faster. And the guy said he didn’t think he needed his computer to be any faster, and left. That’s the only time I can remember anyone saying that to me. It was 30 years ago and I still remember it like it was yesterday.

IBM PC DOS 2000 today

PC DOS 2000 was a harder sell, because by then, the mainstream had moved on. PC DOS 2000 came out during the Windows 98 era. If you needed a standalone DOS circa 1998, then sure, it was a no brainer. But by then the mainstream market was talking about Windows 98 and when it would be time to switch to Windows NT.

But if you have a retro PC made by IBM, and you want to run DOS on it, I think PC DOS 2000 is a no-brainer. The product says IBM as it boots up, so it matches the machine. And if you have a clone that has an IBM motherboard in it, probably a 486 SLC2, you might as well run PC DOS on that. I think it adds to the curiosity.

For that matter, I’ve run it on my other PCs. It never gave me any problems. I go back and forth between running DOS 6.22 on clones and running PC DOS. It seems a bit more authentic to see a clone say starting MS DOS at boot rather than saying starting IBM PC DOS.

But it does work, and I think it is worth considering.

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1 thought on “IBM PC DOS 2000: An underrated DOS”

  1. Of course I agree with you that PC-DOS should be run on an IBM PC or PS/2: There were system BIOS patches of the DASDDRV.SYS, and utilities like QCONFIG (now peeled off for independently running it from other OSes) that are very specific to the IBM systems.

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