ISA video card is slow

I have a computer that contains ISA slots.
I have windows 95 1st release and managed to enable DMA to my hard drive.
Windows accesses my sound card as well through DMA.

WHat I need to know is if it is possible to enable DMA on a video card. I want my games to run faster and as I am playing one, sometimes the page changes 1/2 a page at one time resulting in two halves. Its like moving a picture slowly on another. If it is the refresh rate that is the problem, then what refresh rate should Iuse? My display is configured at 640*480, 256 colors.

Please explain.