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In case it isn't clear to others here, the initial versions of OS/2 targeted 286 systems, so they used the 16 bit extended memory model. IBM never made a 386 based AT, and only released the 386 on it's PS/2 systems that used micro channel, while the PC clone vendors developed the EISA standard and did make 386 based "AT" clones. The later OS/2 2.0 supported 386 and 32 bit flat address virtual address space. Compounding the problem for IBM was that the marketplace assumed that OS/2 need to run on PS/2 and vice versa (the joke was you needed half an operating system to run on half a personal system, a reference to the /2 in the names).
As for Windows NT, it was always 32 bit only (386 or above), there was substantial changes made to the code in order to allow device drivers to run at ring 0 (this was done for performance). Microsoft later reduced the percentage of device driver code that ran in ring 0 with Windows Vista and again with Windows 7, which resulted in slightly slower performance, on my system, for the same game, same settings, frame rate is about 7% slower for Win 7 versus Win XP. These days, blue screens even with WIn XP are fairly rare.
I still have what could be considered a collectors item:
As for Windows NT, it was always 32 bit only (386 or above), there was substantial changes made to the code in order to allow device drivers to run at ring 0 (this was done for performance). Microsoft later reduced the percentage of device driver code that ran in ring 0 with Windows Vista and again with Windows 7, which resulted in slightly slower performance, on my system, for the same game, same settings, frame rate is about 7% slower for Win 7 versus Win XP. These days, blue screens even with WIn XP are fairly rare.
I still have what could be considered a collectors item:
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