From: hpa@casbah.acns.nwu.edu (H. Peter Anvin N9ITP) Subject: Re: VM86 Date: Thu, 3 Sep 1992 16:36:33 GMT
In article <richard.715353503@stat.tamu.edu> of comp.os.linux,
>
> Unfortunately, if this is intended to be a DOS emulator, you are going to
> have to trap the VGA registers that bank the video ram into and out of
> the memory map. This could be made easier if sysv shared memory blocks
> were in place. Create (1M/64K) shared memory blocks, and when the VGA
> registers are twiddled, change the mapping of the memory blocks.
>
> Also, if it were possible to get at the "page dirty" flag, it would be
> very easy to tell which 4K chunks have been modified. This without
> needing to service interrupts. It seems to me that waiting for the
> alarm and checking all 16 pages at the same time would be faster than
> having the overhead of a (several?) task-switch to service each interrupt.
>
A question: since we would need to simulate hardware anyway, why not just
simulate CGA or MDA, at least initially? It would make it a lot simpler,
it seems.
/hpa
-- INTERNET: hpa@nwu.edu TALK: hpa@casbah.acns.nwu.edu BITNET: HPA@NUACC IBMNET: 16331@IBMX400 HAM RADIO: N9ITP NeXTMAIL: hpa@lenny.acns.nwu.edu This is a test of the emergency USENET system.