TestFreaks.com posted a review on the SAPPHIRE ATI Radeon HD 4870 512MB GDDR5 PCI-E Video Card

So yes this is a review of the Sapphire HD4870 with 512mb of ram, but it's also a comparison of what differences, if any there are between having 512mb or 1gig of ram on your video card. I'm comparing the Sapphire 4870 512mb to my Diamond 4870 with 1gig of ram to figure out if it's worthwhile to double the ram or not. Both card run the same 750Mhz Core Clock and 900Mhz memory clock, and both have the 256bit memory interface, they pretty much the same except for the onboard memory.

SAPPHIRE ATI Radeon HD 4870 512MB GDDR5 PCI-E Video Card Review