VGA output scan rates

Getting the relevant information on the chipsets to do this sort of thing is next to impossible. You might look at Linux driver source for this chipset to get the needed info. If you are not up to writing a device driver, then even if you had all the info, you will not get very far.

Regards Anton Erasmus

Hi Mike,

Have a look at Powerstrip

I use it to drive my scart (TV) from a VGA port.

Hans

Mike Warren schrieb:

That probably won't help you much - but Xorg (and XFree86) allow to set (nearly) arbitrary frequencies.

See

for XFree86 information, for a DOS TSR, for general information; maybe helps, too.

Maybe there's something in it for you.

Regards,

Phil

I did this for a company that was selling refurbished fixed-frequency monitors many years ago, so yes it is possible. (Actually I did it on an S3 chipset, which is an ancestor of the Apollo chipset used in the Epia boards).

If you are OK with _only_ getting good video output in Windows, it is not impossibly difficult to write a little program that pokes the CRTC values and simply put that program in your startup folder.

You _MAY_ be able to get by with only poking the standard VGA CRTC locations, but it's unlikely. What I suggest you do is tune XFree86 to the syncrates you want, then dump out the chipset parameters.

Please note that these are interlaced modes requiring the right kind of synch pulses. Some graphical cards are reportedly capable of generating it, some other might not. The low HSync frequency can also be a problem.

Unless you are using monitors with the green extremely slow phosphor, you should limit your vertical resolution to about 240 or 288 pixels to avoid the annoying 30/25 Hz interlace flicker on small vertical details. Practically the same image should be sent to both odd and even frames.

Paul

Thanks for all the answers.

Powerstrip looks promising. Since this is a one-off, the $30 cost is not an issue. I have downloaded it and will try it tomorrow.

-Mike