It has been several months since ATI released the CrossFire platform and started to have a hard time to compete with the already more mature SLI. Last September, when we finally tested the CrossFire, NVIDIA released the nForce 4 SLI X16 that controls dual PCI Express 2x16 slots whereas the nForce 4 SLI and the Radeon Xpress 200 only had to make do with 2x8. Today, ATI comes back with a new chipset that also controls 2 PCI Express 16X slots.
This new chipset named Radeon Xpress 3200, includes a new Northbridge (RD580) that controls 40 PCI Express lanes. Here is the repartition: 2x16 graphic PCIe slots, 4 PCIe 1x slots and one PCIe 4x link to connect to the Southbridge. The 110 nm RD580 chip is simple and power consumption is very low. ATI speaks of 7 to 8 watts.
The Southbridge can else be ATI's SB450 (it unfortunately doesn’t include much of the technologies supported and suffers from a lack of performance with the USB) or a chip from another manufacturer: ULi. This chip supports SATA II 3 Gbps, RAID 0, 1, 0+1, 5, 8 USB 2.0 ports and a 100 Mbps network controller. There is no gigabit network but you just have to add an external controller. There is a small complexity however for ATI as ULi has been bought by NVIDIA. It is a peculiar situation considering the competition between the two protagonists. ATI remained as silent as possible on the Southbridge… The successor of the SB450, the SB460 but mostly the new generation the SB600 isn't ready yet. We heard May, but nothing is confirmed yet. In the meantime, ATI has to make do with the not very interesting SB450 or ULi's Southbridge.
Several manufacturers already announced motherboards based on this chipset: Abit, Asus, DFI, PCPartner and Sapphire.
According to ATI, the Radeon Xpress 3200 is the best choice for gamers. While waiting for a more complete test, we briefly tested it to measure the performance gap with the previous chipset. We used Asus' A8R32-MVP Deluxe motherboard.
With the Radeon X1900 in CrossFire, performance gains are reduced. It is logical because the work of the second card is transferred to the first one via an external cable.
The Radeon X1600 performances gains are more important because the transfer is directly made via the PCI Express bus. Without being exceptional, these gains are significant. We however still have some doubts about the interest of entry level multi-GPU systems whether if they are NVIDIA or ATI.
ATI also speaks of the chipset Overclocking possibilities. It has been conceived with very high tolerance margins. We however haven't noticed significant differences compared to NVIDIA's chipset. While waiting for a more complete test, our opinion on the subject is mixed.
Our opinion on the release today of a Northbridge is mixed too. It is introduced as a high end chip and integrated on high end motherboards, but it mainly bring performance gains for entry level CrossFire configurations (2x X1300 or 2x X1600). Of course, performances aren't reduced and even if gains are small they are here. The Radeon Xpress 3200 replaces the Radeon Xpress 200 and brings better performance. But wouldn't it be more interesting for ATI to wait for the SB600 Southbridge to release a complete platform?