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From: resnicks@netcom.COM (Steve Resnick)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Ms-Dos Source
Message-ID: <1991Apr23.000705.29246@netcom.COM>
Date: 23 Apr 91 00:07:05 GMT
References: <1434@balrog.ctron.com> <1991Apr21.143248.11081@netcom.COM> <1991Apr22.114733.4641@sun1.ruf.uni-freiburg.de>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 38

In article <1991Apr22.114733.4641@sun1.ruf.uni-freiburg.de> hartnegg@sun1.ruf.uni-freiburg.de (Klaus Hartnegg) writes:
>resnicks@netcom.COM (Steve Resnick) writes:
>
>
>>I don't mean to flame anybody, but I have been hearing on the net and 
>>otherwise, that the 80286 doesn't support true multi-tasking, and grow
>>tired of the mis-information about it.
>
>What you are saying here is correct, but...
>
>there are many programs (all that write directly to the screen)
>that won't run in the background on a 286. On a 386 they all work
>fine with DESQview 386. I can even run a graphics programs together
>with a programs that writes to the screen in text mode and have
>both of them on the screen at the same time. And both are running!
>
>This is definitively impossible on a 286.

Although this is true in part, you cannot multi-task MS DOS out of the box
on an 80286. The 80286 hardware supports multi-tasking, but MS DOS, is, 
essentially, a non-rentrant interrupt handler. If you were able to run
MS DOS in protected mode, a protected mode kernel could simply set the
video addresses page table entry to not-present, and handle the
screen I/O as a page fault. My point was that the 80286 hardware does
inherently support multi-tasking. DOS is a different story.

Cheers!
Steve

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