@chunter It's not exactly the same thing, but it's close.

The original PC CPUs (8088/8086) could only address a maximum of 1MB of RAM. DOS was written around that limitation. It reserved 384K of that for itself, and left the remaining 640K available for programs to use. (This is the source of the infamous Bill Gates prediction, "640K ought to be enough for anybody": https://www.computerworld.com/article/2534312/the--640k--quote-won-t-go-away----but-did-gates-really-say-it-.html)

The problem came when DOS programs got so big they stopped being able to fit within 640K. You could add more than 1MB of memory to later PCs, but unless DOS had a way to "see" it, it would just sit there unused.

Two approaches to solving this eventually became popular, one called "extended memory" (XMS) and the other "expanded memory" (EMS). Both could give a DOS program access to memory above 1MB. But they weren't compatible with each other; they each had their own driver, and in some cases needed particular hardware. And programs had to be written to use one or the other. So you had some programs that needed XMS, some that needed EMS, and some that needed one or the other PLUS a guaranteed amount of "low memory" in that original 640K.

So you ended up writing boot loaders for different programs that configured the system memory exactly the way that specific program wanted it. By the end of the DOS era, memory needs had gotten so intense and specific that you could have dozens of these.

Windows solved this by having "real" Windows programs run in protected mode, which was free from the 640K limit, and running old DOS programs in virtual 8086 mode, where you could configure each "virtual 8086" sandbox to have whatever memory configuration you wanted.

@gruff I was a Tandy user myself at that time (Tandy 1000 4 lyfe yo!), so I remember the 2000, though I never had the chance to use one.

An interesting machine, but doomed by the same mistake -- once the original PC became a big hit, if you wanted to sell into the PC-compatible marketplace, you absolutely had to be 100% PC-compatible. "Mostly compatible" wouldn't cut it.

The 2000 sticks out because of the highly unusual decision to go with the 186. Did anyone else actually ship a 186-based machine? That chip kind of got lost in the stampede towards things like protected mode.

@cstanhope In a way, the story of the 286 is the story of the end of an era. It was pretty common in the small-systems world before that for each new generation of hardware to not be backwards compatible with the previous one. It was just expected that you'd have to throw away all your old software when you moved to the next generation.

The 286 was the first time in the PC world that the previous generation had sold enough software (and had software that was being put to enough actually mission-critical purposes) that when people were asked to throw away their old software, they were like, "um, no. No way. Try again."

@Scmbradley By throwing a wrench in the migration away from DOS to a better operating system. The inability of real mode and protected mode applications to coexist on a 286 machine, combined with the huge installed base of 286 machines and of real mode DOS applications, meant that nobody was going to be able to unseat DOS.

Because it had to support the 286, OS/2 was hobbled from the start. Windows didn't really start to take off until version 3.0, when there were finally enough 386 machines in use to create a viable market for software targeted just to them.

IBM's failure to let go of the 286 did give clone makers an opportunity, but for a long time, the 386 machines they were selling were still just running DOS apps in real mode. A complete waste of the chip's potential.

@celesteh IBM never really got the hang of marketing direct to consumers. They had spent 70 years before the IBM PC came out honing their skills at enterprise marketing, and they were still really good at that. But those weren't skills that translated into being able to sell products directly to ordinary people.

When the PS/2 line came out, they spent $50 million to reunite the cast of M*A*S*H in their TV spots. But (1) M*A*S*H had by that point been off the air for years, and (2) they got the cast, but not the rights to use their M*A*S*H characters. So they had them play nameless office workers, which was super bizarre.

Some of the blame of course has to be laid at the feet of IBM's ad agency, Lord Geller Federico Einstein, which had also been behind the Charlie Chaplin-themed ads for the original PC, and which imploded spectacularly two years after the PS/2 campaign.

https://www.youtube.com/watch?v=rbH50T9jxVI