🚀 go-pugleaf

In article <1992Dec27.191516.10755@netcom.com>, samiam@netcom.com (Scott Moore) writes:
>des@inmos.co.uk (David Shepherd) writes:
>
>>Vassilo Walluschnig (Vassilo.Walluschnig@f55.n7101.z5.fidonet.org) wrote:
>
>>:   Okay, I got a question for all those people "in the know" about
>>:   Windows NT. What would happen while running NT on a RISC machine, say
>>:   the DEC Alpha, and running a DOS application in NT, and that DOS
>>:   application makes a direct call to the video card? How would NT go
>>:   about handling such a situation? Would it hang the application
>>:   or would NT come back saying that it cannot run the program and
>>:   promptly shuts the application down?
>
>>i'd expect that NT would stop the program with a memory protection 
>>violation. NT, like OS/2, and unlike DOS is a "real" OS where things
>>like i/o are handled via system calls to drivers ... writing directly
>>to a device register is not allowed.
>
>Ive run serveral applications under NT that write directly to the VGA. They
>simply are slowed down (a little), meaning that some of the accesses are
>being emulated by NT. There is nothing inherently bad about direct hardware
>acess, as long as it is controlled by the OS. This wouldn't apply to the
>RISC case, since there is no VGA to access (I'm guessing character
>mode only ?).
>
>                                         [sam]
>-- 
   In the book Inside Windows NT (Microsoft Press), the archetecture of the new Windows is discussed.  Support for 
Dos , Windows, and OS/2 software is provided by protected sub-systems which act as virtual machines.  The software
is fooled into thinking that it is really runnning under Dos, and this system intercepts all system direct calls.