I have an older 486/66 w/133 AMD proccessor, 64 meg ram, and STB Vision 64 bit video card model CL-GD543x (I think 5434). Tried to overclock by using Fastvid, it helped, about 10% increase, but I get an error when I run Fastvid. It says "DOS/4gw error (2001) exception 06h (invalid opcode) at 160:00440F4E". I tried useing a program called "mclk". It would increase the mghz to about what ever I wanted, but couldn't run Autocad when I did this. Wrong display driver is said.Thanks for any help.