The root cause is that at the time they did an Apple, as they though everyone would run OS/2 or UNIX without any consideration for "legacy" MS-DOS applications, that is why 80286 design never considered this use case worth supporting.

Naturally as history has proven, this was a big mistake.

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canucker2016 4 days ago | parent | next [-]

Intel's 8086 was introduced in 1978. The 8088, used in the IBM PC, was released a year later. Work on the 80286 started in 1978 according to https://timeline.intel.com/1978/kicking-off-the-80286.

There was no CP/M for 8086/8088 CPUs in 1981 which is why Tim Paterson came up with QDOS for Seattle Computer Products. Microsoft's Paul Allen knew about QDOS and acquired it for IBM to use for the IBM PC.

PC-DOS 1.0 was released with the IBM PC in Aug 1981.

CP/M for IBM PC didn't show up until spring 1982.

80286 release date? 1982 Feb 01. Six months after IBM PC/PC-DOS 1.0 was introduced.

By the time the IBM PC's popularity took off, the 80286 design was etched in silicon already.

	▲	pjmlp 4 days ago \| parent [-]
		Might be, but in 1988 the best we could put our hands in Portuguese schools were systems like Amstrad PC1512, 80286 wasn't even on my radar until Windows started to matter. We were happily running MS-DOS 3.3 and DR-DOS 5.0, until it came to be.

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JdeBP 4 days ago | parent | prev [-]

As noted elsethread, there were no "legacy" (an abuse of that word) MS-DOS applications when the 80286 was designed. Intel wasn't really "doing an Apple".

At the time most people were expecting 80286es to become a second higher-end market where people ran Xenix (or perhaps a new MP/M for the 80286), separate from a low-end 8086 market with whatever tinpot non-multiuser non-virtual-memory operating systems were going to come out for it.