<CT> Insight from DPMI

  • From: Alan Grimes <alangrimes@xxxxxxxxxxxxx>
  • To: calmira_tips@xxxxxxxxxxxxxxxxx
  • Date: Mon, 19 Mar 2001 16:47:05 -0500

Hey, Last week I ordered the DPMI 1.0 specification from Intel. (Win3
implements parts of 0.9). It just arrived. =)

From looking it over I have gained some insight to exactly how
multitasking works under windows. 

The DPMI system allows for multiple 16-bit and 32-bit programs to
operate within one or more virutal machines. 

There are two limitations on this system that have direct effect on how
windows works. 

Firstly, modular software that consists of numerous shared components
(.dll files, and the core .exe files of windows) must exist within a
single virtual machine. That means that for a windows program to access
windows services it must reside in the same Virtual Machine. Since there
is no way to segregate programs within the same virtual machine, you
can't prevent the spectacular cascade failures you often see with 'doze
3.11. =(

Secondly, virtual machines are not multithreaded meaning that you cannot
have pre-emptive multitasking within them. =(

I'm going to study it in detail and see how best to fix these

People who work on computers use linux; People who work on life use
Macintosh =)
http://users.erols.com/alangrimes/  <my website.
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