Sapphire Radeon HD4870 512MB Graphics Card Review
 

The Sapphire Radeon HD4870 512MB graphics card may look just like a unit from the HD3870 series, but it is a top of the line model offering a PCI Express X16 interface, a 750MHz core clock, and 900MHz GDDR5 memory which makes things very interesting thanks to the greatly increased bandwidth (in comparison to GDDR3 and GDDR4).

http://www.bigbruin.com/2008/sapphire4870_1