>Can some please help me config my video card for X11R6. I have an
>STB Velocity 64VL video card with 2MB dram. The video card has an
Are you sure about that? ---------------^^
I really don't think they ever put Dram on that model.
Quote:>S3 Vision 968 chip on it. The monitor I'm using has horizontal scan
>freq of 31.5-60 and vertical of 60-75 non-interlace.
README.S3 told me everything I needed to know about setting up XFree86
for that card. VideoModes.doc covers what you need to know to set up
modelines. I thought it was a little verbose, though, so I put
together some notes on generating optimal modelines. Hopefully
they will be helpful. Of course, any time you play with video modes,
make sure you keep them within the specs of your monitor, or you could
The thing you usually have to worry about is keeping your hsync rate within
the monitor's spec. Also, keep vsync within the monitor's spec and keep
in mind that image quality may deteriorate if the Dot Clock Frequency (DCF)
exceeds the monitor's bandwidth rating. If you enter the correct ranges for
your monitor in XF86Config, the server will protect you from straying
outside the monitor's range.
Here are some useful equations I gleaned/extrapolated from VideoModes.doc:
Here is a typical modeline:
Modeline "1152x864" 110 1152 1200 1392 1448 864 870 872 907
# DCF HR HG1 HG2 HFL VR VG1 VG2 VFL
Hsync = DCF / HFL
DCF = Hsync * HFL
RR = DCF / (VFL * HFL)
BW = BandWidth; the maximum dot clock frequency the monitor can handle
without sacrificing image quality. This can be viewed as a soft
guideline, while Hsync and Vsync (Refresh Rate) are hard limits.
Hsync = Horizontal Scan Frequency in KHz
Vsync = Vertical Scan Frequency in Hz, or Refresh Rate
DCF = Dot Clock Frequency in MHz; should be <= monitor bandwidth
HR = Horizontal Resolution (number of viewable dots/stripes in a row)
HFL = Horizontal Frame Length (number of dots/stripes in a row, including
those outside the viewable area); typically, HR + 20 to 30 percent
(about 25% seems to work best for me).
Increase this to make the image narrower, decrease it to make
the image wider.
IMPORTANT: If you decrease this, you may have to decrease DCF
as well, to keep Hsync within the monitor's specs!
HG1 & HG2 = Horizontal "Guards"; allows you to center the display
a good starting point seems to be: HG2 > HG1 and
HG1 = HR + 32 and HG2 = HFL - 32
VR = Vertical Resolution (number of viewable rows of dots)
VFL = Vertical Frame Length (number of rows, including those outside the
viewable area); typically, VR + 2 to 7 percent
VG1 & VG2 = Vertical "Guards"; Allows you to center the display vertically;
A good starting point here seems to be:
VG1 and VG2 centered between VR and VFL and VG2 - VG1 = 8
RR = Refresh Rate in Hz
Without a timing chart for the monitor, the "Guards" are really just a
guessing game. If someone knows how to make better "best guesses" for
these, please share it. Anyway, this should give xvidtune something to
To get the best refresh rate your monitor can handle at a given resolution:
- Calculate HFL for that resolution
- Calculate DCF, using the max Hsync your monitor can handle
- Fill in the rest of the modeline
- start X and use xvidtune to fine-tune the size and centering
As you are doing this, keep an eye on the Horizontal sync to make
sure you don't push it beyond what the monitor can handle. If you
"run into the wall", drop DCF a little and try again.
- put the new "tuned" values into the modeline
Please let me know if you have any observations or suggestions that
could help make these notes better.
Don Dettke, Software Engineering Consultant