Linked by Thom Holwerda on Sat 9th Feb 2013 18:54 UTC
Windows "The 16-bit Windows kernel was actually three kernels. One if you were using an 8086 processor, another if you were using an 80286 processor, and a third if you were using an 80386 processor. The 8086 kernel was a completely separate beast, but the 80286 and 80386 kernels shared a lot of code in common." As always, Raymond Chen delivers. If you don't yet follow his blog, you should. Right now. Click that bookmark or RSS button.
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moondevil
Member since:
2005-07-08

By the standards of the day, I suspect DOS worked as well on the 286 as it did on the 386. But yea if by modern OS you mean something that used protected mode for process isolation and timeslicing, then 386 was the first serious intel processor for that.

It predates my experience, but my understanding is that the 286 included a very buggy form of protected mode, and lacked VM86 real mode virtualization. The silly engineers at intel failed to include a way to switch the processor out of protected mode, so the chipset makers actually incorporated external logic to do a hard reset on the processor every time one needed to switch between real mode programs.

So this is how windows multitasked on the 286, by continually rebooting the cpu - a feature MS continued to include a couple generations later. I kid ;)



You got it wrong. Let me explain as I was already a long time computer user on those days.

The 80286 already had everything a CPU needs for modern operating systems, at least 16 bit ones.

What happened was that Intel thought everyone would be so amazed with the possibilities of protected mode, that no one would care for real mode any longer, hence the no inclusion of programming instructions to switch back to real mode.

But MS-DOS users were reluctant to go 100% to Windows 3.0, specially given the hardware restrictions, lack of software and the novelty of the GUI for many of them.

So Microsoft needed a way to keep MS-DOS applications running inside Windows 3.0, that is how the continuous reset on Windows came to be.

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