Radeon HD 4870X2 is the high-end part of the Radeon HD 4000 series. Like the Radeon HD 3870X2 it sports two linked GPUs on a single PCB. The exact nature of the link is unknown, but we’ve been told that AMD has done some major changes to the linking since the last generation, since AMD was quite displeased with the performance of the 3870X2 bridge chip. According to a recent post at VR-Zone, citing a source who does not want to be named by name, Radeon HD 4870 will not suffer from microstuttering since the communication will be done through the memory instead of a bridge chip. This should also have a positive effect on the CrossFireX performance.
Microstuttering is a result from using AFR (Alternate Frame Rendering). The frames are then sent to the monitor at an uneven rate (more like two and two instead of a steady flow) which causes stuttering. Running two Radeon HD 4870X2 in CrossFireX for three or four GPUs should still have the same rendering problems though, I.e. if AMD hasn’t come with another new feature for the Radeon HD 4000 series, but we’re skeptical there.
There will also be Radeon HD 4850X2 cards which will instead use GDDR3 memory and lower clocks overall, but this is an optional card for partners. The performance of this card will of course vary depending on the clocks, but it should still be in the high-end part and able to compete with the GeForce GTX series, while the 4870X2 and its GDDR5 memory is estimated to beat the GTX cards with a margin. Both cards are slated for a fall launch.
