Bigbruin.com has posted a review on the Sapphire Radeon HD4870 512MB Graphics Card

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).

Sapphire Radeon HD4870 512MB Graphics Card Review