Re: 640x512x16bpp with VESA ?


"whygee" wrote:
Hello,
Hi,

I have to use a 1280x1024 screen but there are too many pixels
to compute there. I think that a halved resolution would fit
but 1:1.25 ratio modes are very scarce. Practically, I use
the VESA2 framebuffer in ASM with my own bootloader so the
help of an operating system is useless, unless it gives me
correct parameters. Should I dump the registers after X.org
has set this mode ?

Dunno what X.org does nor what it is ...
but I also have to use VESA/VBE to set Vmodes on newer PCI/AGP cards,
because they are unfortunately not at all documented in deep detail.

I guess that I have to setup 1280x1024x16 then tweak the CRTC

by x16 you mean 16 colors on four distributed planes ?
or 16-bit colours ?

to "double scan" (so i get 1280x512). I have read books 12 years
ago about this but i don't remember the particularities of the X mode :-)
I have to half the clock speed too but it's above my ability now
(i don't have the books anymore). Hint : my graphics chip is based on S3.

It will not be enough to set Vclock and double-scan, you need also
to recalculate synch/border/blank periods within the range of your
monitor.
I remember good old S3-times quite well and I played around with
own created Video-modes of any kind, even a weird behaving mixed
Text/Graphic-mode were possible here.

My requirement is to conserve the 1:1.25 ratio of the screen
with practically fine values. If you know of other resolutions
that fit, fine, as long as I can set it with a simple asm program.

You got a 5:4 (better known as 10:8) monitor ?
I never used any 4-bit color format, my preference is and always was
8-bit (one byte/pixel serves me well) and my standard resolution is
1152*864x256 to allow a 1024x768 display plus tool-bars and stuff,
so keeping the monitors 4:3 format (and circels remain 'round').

I once found all required information for S3(GL4x/5x..)in RBIL(ports).
This collection may be still on one of my old HDs, so if you don't
find it on the net, I could search my archives and post the few pages.

Do you know which S3-chip is in there ?

thanks,
YG (not been here for 8 years or so...)

welcome back ;)
__
wolfgang


.

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