Fudzilla: "XFX was working hard to bring AMD cards to the market while waiting for Nvidia's Fermi. They launched a bunch of AMD Direct X 11 cards starting from the smallest and cheapest HD 5450 which will costs you €35 all the way up to the currently priciest HD 5970, for the price of which you can get as many as fifteen HD 5450 cards. But, XFX is mainly known for their overclocking business, and they're always among the first to jump aboard the overclocking train. XFX took only the creme of the crop Cypress LE chips and created its HD 5850 Black Edition series of cards. Of course, Black Edition naming scheme says that the card comes overclocked.
The HD 5850 Black Edition's core is up from reference 725MHz to 765MHz, and the memory up from 1000MHz (effective 4000MHz) to 1125MHz (effective 4500MHz). So the card's GPU is some 5.5% faster than reference, whereas the memory is 12.5% faster than reference."