As is customary with most technology the best revisions and refinements usually come around at the end of a product’s life, this time around is no different. The XFX Radeon HD 4890 Extreme sports a mild factory stock overclock and, with a bit of prodding, may just hit those high speeds you desire.

HardOCP has a review:

Taking it a step further to see just how much farther we could get, we increased the fan speed from auto to manual and set it at 100%. With this, we ended up with a fantastic clock speed 990MHz on the GPU and 4.68GHz on the memory without any voltage modifications!

Speedy, but you may want to save up a bit more and go for the latest and greatest.