Mail Archives: djgpp/1998/01/28/15:45:54
>Is there any possibility to access the SVGA chip without
>using the VBE in DOS?
Of course! But you should be aware that there is no single "SVGA chip",
but many hundreds of different and incompatible pieces of hardware, so
you will have to write special code for each card that you want your
program to support.
There is some basic information on the more common chipset families in
the PCGPE, and a much more comprehensive set of specs in the VGADOC
package, both of which can be found on x2ftp.oulu.fi. And my Allegro
library contains native hardware drivers for a few cards (currently the
ATI 18800/28800/Mach64, Cirrus 54xx/64xx, Paradise, S3, Trident, Tseng
ET3000/ET4000, and Video7 boards), which might be useful for you to look
at. But be warned that although Allegro has been in development for
several years now, and many different people have contributed drivers,
it still only supports about 10% of the cards in the world! Writing
native SVGA code for all cards is a huge task, which is why I think VESA
is such a good thing...
>I'd like to use the chip's additional features like drawing, bitblt,
>areafill, clipping, lfb, etc... (VBE doesn't support these functions)
VBE 2.0 doesn't support them, but VBE/AF does. At present SciTech have
implemented /AF drivers for ATI, S3, Tseng, and I think Cirrus boards,
and promise much wider support in the next version of UniVBE. The VBE/AF
spec is currently only available by purchase from the VESA people (see
www.vesa.org for details), but SciTech told me that they are agitating
for a public release of the standard, and VBE/AF 2.0 will probably be
freely distributable. I think it is a very nice and well designed API,
keeping all the good things about VBE 2.0 while discarding most of the
problems and legacy 16 bit code, adding OS portability (a VBE/AF driver
could theoretically be used under Linux, or indeed any protected mode
i386 system), along with a relatively painless way to access hardware
accelerator features. I really hope that this will become an established
standard for DOS graphics, and the only reason I haven't already written
a VBE/AF driver for Allegro is that I am still waiting for SciTech to
implement it on my Matrox card :-)
>I've heard somewhere the GGI project will be ported to DOS.
The last I heard was that there were no plans for doing this, and I was
told that there are a lot of interdependencies between the GGI driver
code and the Linux kernel, so it might be very difficult to port. I
might be totally mistaken about that, but in any case the GGI project
isn't nearly far enough along to be useful for present-day development.
--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
"Pigs use it for a tambourine" - Frank Zappa
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