2005-08-29
Article Rating:
/ 0
| Table of Contents: |
| Rate This Article: | Add This Article To: |
|
( Page 7 of 7 )
's CrossFire Works"> The CrossFire supports three primary performance modes of dividing up the processing workload: Scissor, SuperTile, and Alternate Frame. The first type, scissor, divides each frame into top and bottom halves. Each GPU is tasked with rendering one half of each frame.
SuperTile, the second type, splits each frame into 32 x 32 pixel tiles like a chess board. This is superior solution to scissor in terms of load balancing. It's possible, for example, to load a single processor more heavily in scissor mode if a lot of action is taking place in the bottom half of the screen. The unloaded GPU is forced to wait for the other, and resultant performance is suboptimal. The SuperTile configuration partitions the screen with better granularity, allowing GPU processing loads to be distributed in a more even fashion.
The third mode of operation, alternate frame mode, splits the workload frame by frame. GPU 1 renders all the odd frames, while GPU 2 renders all the even frames. This mode allows full geometry acceleration.
Another feature ATI spent some time plugging was its SuperAA Image Quality mode. Allowing up to 12x and 14x AA with dual-GPU antialiasing, the approach takes multiple samples per pixel to determine the best sample pattern. Individual strands of hair, for example, can sometimes be less than a single pixel wide. ATI claims that its SuperAA's robust sample pattern will effectively smooth out this type of micro-geometry and add finer detail to object contours. We can't wait to find out how it stacks up against Nvidia's SLI "16x" AA solution.
Finally, ATI's CrossFire provides a little more flexibility when it comes to video card selection. You can link any two of the Radeon x850 family cards together to get the CrossFire benefits. Same goes for the Radeon x800 card family.
The final bit of flexibility offered by ATI is validation of CrossFire graphics cards on motherboards using Intel chipsets. Currently, two motherboards using the Intel 955X chipset are shipping with two PCI Express x16 slots. ASUS is shipping its P5WD2 series, while Intel is shipping the D955XBK.
The major issue for ATI, though, is ship dates. Several OEM contacts informed us that CrossFire was probably a month away from shipping, so it looks like CrossFire may ship at roughly the same time as the new R520 GPU. We'll have to just wait and see.
This article was originally published on extremetech.com.
>>> More Microsoft Architecture Articles >>> More By Victor Loh
