I am interested in an app that is stated to require a '32-bit video
card'. How can I determine if my PCI card satisfies that?
Thanks
Duke
Once the video card driver is installed, the Display Control Panel
should show the color options. This card is currently set to
1024 x 768 (a 15" monitor screen perhaps) and 32 bit color depth.
http://www.tweakguides.com/images/ATICAT_5s.jpg
At one time, there were restrictions on color depth versus resolution.
Color depth required more memory on the video card. We used to pay
a fortune to fix that (my most expensive video card was $1000, so I
could get full color depth). Now, that is a joke, and a $35 card
can do everything and more, than that old $1000 card.
Sometimes, you can find a manual or spec sheet, and see how modern
cards have removed the limits.
The end of "Table A.1 GeForce FX Modes" shows the upper limits of some
six year old cards.
ftp://download.nvidia.com/Windows/53.03/ForceWare_Release_Graphics_Drivers_Release_Notes_WinXP2k_53.03.v3.pdf
Resolution Color_Depth Refresh_Rate (60Hz for LCD, more for CRT)
---------- --------------- -----------------------------------------
1920x1440 8, 16, 32 60, 70, 72, 75, 85
(Notes) iii iv,v
2048x1536 8, 16, 32 60, 70, 72, 75, 85
(Notes) iii iv,v
iii. Requires at least a 16-MB framebuffer for spanning modes (obtained by
doubling either the horizontal or vertical resolution).
iv. Requires at least a 32-MB frame buffer for spanning modes (obtained by
doubling either the horizontal or vertical resolution).
v. Requires a 16-MB framebuffer for the Windows desktop. 3D applications
generally require more than 16 MB.
Since modern video cards tend to have quite large frame buffers, having room
to store a high resolution and high color depth frame buffer is not a problem.
The resolution and refresh rate, affect the DAC bandwidth needed, but
modern cards are rated at 400MHz analog bandwidth, and numbers like that
2048x1536 are possible on VGA. (DVI limitations are a separate issue, and not
as well documented.)
At one time, 32 bit color meant 24 bit color plus an 8 bit overlay plane.
So the RGB colors were just 8 bits each.
If you look at a DVI cable, you can see a similar pattern. This is the digital
data used to represent one pixel on the screen. The two bits at the end, are for
TMDS transmission encoding (makes the cable work better, in a sense). You can
see in this example, that a total of 24 bits defines that one pixel. This
pattern can repeat, up to 165 million times a second, on the DVI cable.
(The bits are all the same width, and the ones on the end are bigger, so the
labels would fit
)
_____________________________ __
DVI_clock ___| |_____________________________________|
_____ _____ _____ _____ _____ _____ _____ _____ _______ ___________
Red |__0__|__1__|__2__|__3__|__4__|__5__|__6__|__7__|__XNOR_|_DCBALANCE_|
_____ _____ _____ _____ _____ _____ _____ _____ _______ ___________
Green |__0__|__1__|__2__|__3__|__4__|__5__|__6__|__7__|__XNOR_|_DCBALANCE_|
_____ _____ _____ _____ _____ _____ _____ _____ _______ ___________
Blue |__0__|__1__|__2__|__3__|__4__|__5__|__6__|__7__|__XNOR_|_DCBALANCE_|
There are some other possibilities now. I've heard of "deep color", which may
offer even more bits per pixel. It is all a question, of what the monitor
would do with it. Like audio, it begins to lose meaning, if you go overboard.
http://en.wikipedia.org/wiki/Deep_Color
Paul
