change screen refresh rate

hello!

i need to write a little dos program to change the screen refresh rate in svga mode (640x480x256 up to 1024x768x256).

the grafic chip is only vesa v2.0 compatible so i think i have to program the chip (NS CS5530A) directly.

what registers i have to look for? i am not so into assembler... :(

Comments

  • : hello!
    :
    : i need to write a little dos program to change the screen refresh rate in svga mode (640x480x256 up to 1024x768x256).
    :
    : the grafic chip is only vesa v2.0 compatible so i think i have to program the chip (NS CS5530A) directly.
    :
    : what registers i have to look for? i am not so into assembler... :(
    :

    Have you picked up the datasheet for this part?
    I think this is the one you're working with:
    http://www.national.com/pf/CS/CS5530A.html

    After looking through it briefly, you need to first find the base address of the "F4BAR" block of memory space. The base address is located in PCI config of function 4 of this chip. (offset 10h)

    Once you get the base address in memory space, it looks like base+24h has the stuff you'll want to tweak to get the freq changed. How exactly to change that to the freq you want will be up to you. ;)

    If what I just said makes absolutely no sense to you, send me a private mail or post questions here and we'll get you where you need to go.

    -jeff!
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