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The itsy bitsy north bridge
That's not the say that the CrossFire Xpress 3200 isn't an impressive piece of hardware. In spite of the fact that it has several superhighways worth of PCI Express lanes running through it, this may be the smallest north bridge chip we've ever seen—assuming the term "north bridge" is still appropriate for a chip that has no memory controller or front-side bus onboard. TMSC manufactures the RD580 for ATI using a 110nm fab process, and its 22 million transistors fit into an area only 22 mm2. ATI estimates the chip's TDP at only 8W, a number that seems practically revolutionary in the world of power-sucking dual-graphics behemoths.


The CrossFire Xpress 3200 is tiny

A small chip made on a relatively advanced fab process with low thermal dissipation requirements sounds like a perfect recipe for some overclocking, and ATI seems to agree. They claim that "all logic is massively overspecced" on the RD580 to allow ample overclocking headroom. The HyperTransport link to the CPU, they say, is optimized to run at speeds 50% faster than stock, while PCI Express is ready for up to 40% overclocks—all with little or no extra voltage. The red team has earned itself some major credibility on this point with the Radeon Xpress 200 or RD480, this chip's predecessor. We reached HyperTransport speeds of 325MHz in our testing of the Asus A8R-MVP, the A8R32-MVP Deluxe's forerunner. Like that board, the A8R32-MVP cools its north bridge with nothing more than a medium-sized passive heatsink.


ULi's M1575 south bridge

Expect most CrossFire Xpress 3200 motherboards to ship with a south bridge chip from ULi rather than ATI's SB450. The SB450 has been plagued with USB and PCI performance problems throughout its history, and most mobo makers appear to be going for the ULi M1575 south bridge as a result. ULi has endowed the 1575 with just about all of the features a modern I/O bridge might need, including support for SATA 3Gbps transfer rates, Native Command Queuing, RAID levels 0, 1, 0+1, 5 and JBOD, and High Definition Audio. The chip sports four PCI Express lanes to link it to the RD580 north bridge, making it an ideal choice for the A8R32-MVP Deluxe—except for one thing.

NVIDIA just bought up ULi, making the M1575 a wholly owned NVIDIA product. ATI says it's confident that NVIDIA will elect to continue supplying the M1575 in adequate volumes for CrossFire Xpress 3200 motherboards because large customers like Asus will demand it. I can see the logic in that point of view, and they may well be right—unless they aren't. Even if NVIDIA doesn't constrain supply of the M1575, though, they might have some fun with it. Personally, I'd rename the chip "nForce M1575 Whozyerdaddy" and supply all they wanted.