I have visiontek radeon x300 pci-e video card with active heatsink. How fast can I overclock this GPU no fan?

There is not set amount, depends on the specific chip, and I don't mean model I mean the actual specific chip on your card. Watercooling will always help overclock better.|||I don't know for certain about your computer, but I have the exact same card and it did NOT take well to overclocking. Just citing personal experience, I would avoid it altogether.|||I would do 510/460...|||400/210, then it starts to have errors. i have one and it is stable at that speed using ati tool, with no fan. if you added a pci fan directly on it, im assuming you could get it to be stable at a little higher speed. seriously, though, its not a great card, for very little money you could get a better card.