Re: Video Mode 13h in windows XP ... impossible?

From: wolfgang kern (nowhere_at_nevernet.at)
Date: 02/19/04 

Date: Thu, 19 Feb 2004 21:40:56 -0000

Beth answered da_buddha:

[about Vmode13 PM]

Beth described the 'standard way' of graphic-access
while in protected mode, which make use of the DOS-box.
For a beginner this is a good way to achieve first
satisfying results.

For me (the speed freak) this is a detouring slow way.
Here is a faster method:

Perform this four steps in the DOS-box only once.

1. check if your graphic card support VBE+2.0 (int10 4f..)
2. search for the mode13h VESA-alias 640*480,256
   in the mode-list (by features rather than VESA-number)
3. check if this mode can be "layed flat" (linear VRAM-space)
4. check if the V-BIOS support PM32 mode-set and start-address,
   then get the PM-entry point.

If all above questions result positive,
you now may change Vmode without leaving PM,
and you can direct write direct to the whole Video-memory.
This allow much faster mode-changes and access
to all of the V-RAM (not limited to 64/128KB aperture at 0A0000..).

For example my 8MB VRAM give me (direct and consecutive accessible)
27 pages of 640*480,256 that way.
Many 'faster' games use a larger play-field (ie:3200*2400,256)
as a permanent resident map to let you extremely fast scroll through,
by just altering the 'screen-start' address.

confusing? perhaps.., but isn't fast graphic the target?

My (fastest) way is using direct hw-access,
but this goes a bit deeper and needs hardware specific routines,
so I can only support a few known cards that way,
for all 'unknown' stuff I have to use VBE/VESA method.

And Beth is right, end all your DOS-session with int10 ax=0003,
otherwise the DOS-window may show wrong font garbage.
__
wolfgang

Relevant Pages

  • Re: input & output in assembly
    ... Mr Dygi wrote: ... >> not in protected mode. ... Maybe Beth can do this. ... programming, you have to read the processor manual anyhow: ...
    (alt.lang.asm)
  • Re: input & output in assembly
    ... Mr Dygi wrote: ... >> not in protected mode. ... Maybe Beth can do this. ... programming, you have to read the processor manual anyhow: ...
    (comp.lang.asm.x86)