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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Alfman
Member since:
2011-01-28

moondevil,

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

I actually agree with everything (else) in your post, but was anything factually wrong in mine? It's definitely possible but your response didn't make it clear what is wrong.

I find it very strange how intel failed to anticipate the need for a mode switch, but mainboard manufacturers did by implementing the external 286 reset logic. Was there an early generation of 286 mainboards which didn't support a cpu reset?

Reply Parent Score: 2

moondevil Member since:
2005-07-08

Your comment:

So this is how windows multitasked on the 286, by continually rebooting the cpu


This was only required if you needed to start a MS-DOS program from inside Windows. Otherwise it was running in full 16 bit protected mode with all required features.

Was there an early generation of 286 mainboards which didn't support a cpu reset?


I am not sure, but that could have been the case with Xenix systems, which did not require MS-DOS compatibility.

Reply Parent Score: 3

Alfman Member since:
2011-01-28

moondevil,

"This was only required if you needed to start a MS-DOS program from inside Windows. Otherwise it was running in full 16 bit protected mode with all required features."

Yes of course, software could be built for the 16bit protected mode. If you want to say the 286 was capable of multi-tasking, then I'll have to admit that it's technically true, but it required all software to be rewritten for it. The 386 was intel's first processor suited for general purpose multi-tasking, that's my opinion anyways because the 286 needed external chipset logic to continuously reset itself into real mode to run the majority of software avaiable at the time.

Edited 2013-02-10 21:04 UTC

Reply Parent Score: 2

Megol Member since:
2011-04-11

moondevil,

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

I actually agree with everything (else) in your post, but was anything factually wrong in mine? It's definitely possible but your response didn't make it clear what is wrong.

I find it very strange how intel failed to anticipate the need for a mode switch, but mainboard manufacturers did by implementing the external 286 reset logic. Was there an early generation of 286 mainboards which didn't support a cpu reset?


No. There could perhaps be mainboards that doesn't support the reset protocol needed but that's unlikely.
Doing the reset itself can be done in software without extra hardware by triggering a triple fault, just load the interrupt description table pointer with something faulty and then do a software interrupt.

Reply Parent Score: 2

Alfman Member since:
2011-01-28

Megol,

"Doing the reset itself can be done in software without extra hardware by triggering a triple fault, just load the interrupt description table pointer with something faulty and then do a software interrupt."

Ah, very clever! And here I was thinking it was an oversight by the bastards at intel, how wrong I was. My faith is restored ;)

Reply Parent Score: 2