> xxxxx@lists.osr.com wrote on 02/21/2005 07:16:03 PM:
Mats PETERSSON wrote:
> Just beware that the screen may not be represented in a linear
pixel-format if you have a fancy graphics card.
In the bad old days, I wrote networked TSRs (well, DECnet anyway :-))
that wrote to video memory at b800(b8000?) to communicate messages to
the user. I have not done anything with video since then (and if you
know what a TSR is, you realize how long ago that was). Are you saying
that (writing to b8000) won’t work any more? I know it won’t be visible
if Windows is running, but this is while a driver is loading, no? I
think I missed the Original.
Yes, that would work, as long as the card is in VGA-text mode.
I was more commenting on the case where the graphics driver is active (the
previous post was talking about “drawing pixels”, so I took it to mean that
the driver was actually running in parallel with the display driver, rather
than BEFORE.
Our graphics cards do not necessarily store pixels in a linear format, even
on the display (it normally does, but it is possible that it DOESN’T), so
if you poke a byte/dword into a memory location at the beginning of the
screen, and just continue incrementing the address, it’s not necessarily
going to draw a line of pixels at the top edge of the screen.
Because graphics processors often work on “lumps of pixels”, it’s not
necessarily the best idea to address them in a straight linear fashion, and
we’ve got other ways to address the “lumps”.
[Oh and forget the idea that a 1200 pixel wide screen actually has a stride
of 1200 * pixel-size, it may be quite different].
But as long as it’s using the VGA driver, it will of course work like a VGA
card in backwards compatible mode.
–
Mats
Just trying to find out how out-of-date my knowledge is,
Thanks,
ScottR
Questions? First check the Kernel Driver FAQ at http://www.
osronline.com/article.cfm?id=256
You are currently subscribed to ntdev as: unknown lmsubst tag argument:
‘’
To unsubscribe send a blank email to xxxxx@lists.osr.com
ForwardSourceID:NT0000D6FA