Running a utility to change screen modes in AUTOEXEC.BAT would be easier than hacking the BIOS, if you don't need to interact with anything before that.

AFAIK all the standard text modes are 70hz. If you set a graphic mode instead of text then DOS/BIOS functions can still display text but they become much slower. You'd have to mess with VGA registers to make a custom text mode, or see if the video card supports a VESA or nonstandard 60hz text mode through its INT $10 interface.

Or maybe you could run the Japanese DOS/V which uses 640x480.

You can use VGA240 to switch to 60Hz, some info here: http://nerdlypleasures.blogspot.com/2018/02/s … cap-review.html
It does add borders, perhaps this can be solved with the OSSC.

This of course doesn't work directly on boot (accessing BIOS etc), but like bakemono said, add it to AUTOEXEC.BAT and your DOS session is good to go.

Try this one.

Not sure if it works in text-mode, too, however.

Thanks! I will try your suggestions. To set the refresh in the autoexec file is a good option.

I will keep digging into BIOS hacking, although with these old video cards (cirrus VLB,trident 9000i is what I have at hand) the information is scarce.

BCH wrote:

I will keep digging into BIOS hacking, although with these old video cards (cirrus VLB,trident 9000i is what I have at hand) the information is scarce.

It's not going to be easy. Each VGA card has its own BIOS. You'd have to dump the VGA BIOS, then reverse-engineer it to find the video mode setup. Then you need to patch that code, create a new ROM image, and flash that into an EPROM, and replace the ROM on the card.