Whats wrong with my 4850's memory clock???

I was browsing on newegg and saw all the 4850's had a 1986mhz memory clock and i especially like the visiontek one. I went to Best Buy and bought one and put in my system. I bought a visiontek just like the one on newegg. Well, the memory clock is only 993mhz. Why isnt it 1986mhz??? I am running this card on a PCI-E x16 1.0, not 2.0. is that the problem?? Is my 4850 just a piece of **** compared to the others???