RE: [plex86] Performance enhancement: elminiating mode and context

[Bart Oldeman]

On Mon, 18 Dec 2000, Drew Northup wrote:

> I'd have to agree here--for the most part.  A good example of this is how
> old DOS programs did curses-style GUI in DOS-MODE (no windows yet--XTREEPRO
> for instance I think does this).  Many people here know about the IAPx
> screen character buffer.  This is MMIO by most definitions--although it
> isn't handled directly (the IO part is done by hardware), but it is still IO
> that plex86 needs to catch and redirect.

Nope: text screen buffers can just be written to directly by the
guest: the monitor just needs to update the real screen every once in a
while.

Screen buffer is at 0xb800:0 or 0xb000:0 in guest space, plex86/whatever 
can just read this, and produce characters on a graphics display.

You only have MMIO like buffers for VGA if it's in a planar mode
incl. 640x480x16 and mode-X, and even then it depends on the values of the
VGA I/O registers.

Bart