X1900XTX Crossfire Performance

The main selling point of Xpress 3200 and the ASUS A8R32-MVP is that both video cards will be able to run at x16 when in Crossfire mode.

The question for me was whether high end video cards will actually benefit from this. To test this the motherboard was set to x8/x8 via the BIOS. Other reviewers compared Crossfire performance to an RD480 board, but this will be affected by performance improvements between these chipsets, BIOS and BIOS settings as well. For additional reference a X1900XTX in single mode was tested too.


Apparently there are no gains to be seen in those two tests. Like most applications, 3DMark and FEAR upload all geometry and texture data to the video card once and the card renders from there, so the bus is barely used. Another reason is that many games are CPU limited with such high performance video cards, your money might be better invested in a faster CPU then.

The best gains can be expected when there is a lot of PCI-E traffic going on. This is the case in bridge-less Crossfire setups like they are possible on the Radeon X1300 and Radeon X1600. Another setup that will see nice gains is when the renderdata will be copied to the CPU every time, for example to do AA when rendering HDR output. Many upcoming games will use that.