Crossfire Hardware Specifics

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New graphics boards paired with old

The biggest deal with Crossfire is that it works with existing PCI Express-based X800 and X850-series Radeons, powered by either R423 or R480. While that's no help to an AGP Radeon X800 or X850 consumer (and it's the same for NVIDIA), for those of you that've made the jump to PCI Express already, you can use the board you have (if you wish). In either scenario, whether you have an existing board or you want to start from scratch with Crossfire, the master board that you purchase determines what slaves (existing boards) it can work with, and vice versa.

The way it works is simple. There will be three Crossfire Edition boards available to buy: X850 Crossfire Edition 256MiB which works with all X850-series PCI Express Radeons and a pair of X800 Crossfire Edition boards that work with the X800-series PCI Express Radeons, one with 128MiB of memory and one with 256MiB of memory. The X850 Crossfire Edition doesn't work with the X800 Radeons and the alternate combination (X800 Crossfire + X850 existing) isn't supported either. However, if you satisfy those conditions, you can use the Crossfire Edition board with any compatible board, from any vendor, with any VGA BIOS. No need for matched hardware in that respect, according to ATI.

Pairing R423-based X800 Crossfire Edition with R423-based X800 existing boards, and the same with the R480-powered X850 series of boards, lets ATI keep compatibility issues to a minimum, while also forcing your hand a little with what you can buy, in return.

New mainboards to put Crossfire hardware into

Like with NVIDIA's SLI, you'll need supporting core logic to make Crossfire work properly. ATI have Crossfire Edition Radeon Xpress 200 core logic variants for both Intel LGA775 processors and Socket 939 AMD Athlon 64 and Athlon FX. The core logic is new, which means an existing investment in any other PCI Express core logic will have to be sold or squandered, in order to switch. New customers will have it best.

With both Crossfire Edition graphics boards and mainboard hardware, ATI has a large partner list that'll be producing what's needed. I'll announce a full parter list after Computex starts.

Questions of output

Since there's an external dongle to connect master (Crossfire Edition) and slave boards, from the slave boards DVI output to the master DVI output of the Crossfire Edition board, that still gives you two DVI outputs to connect displays to, one on the Crossfire Edition board's backplane and one on the dongle. It'll be interesting to clarify just how those two outputs (or DVI + VGA with convertor on the dongle) can be combined with SurroundView on the Xpress 200 core logic for three-head output, if at all possible.

Again, the docs are pants, but it appears as if three displays can indeed be connected in that way. Indeed, the documentation shows up to 5 outputs (2 per board, one on the mainboard) are possible, but that's obviously not available in Crossfire mode (although it's doable on a Crossfire Edition mainboard). I'll keep you posted during Computex and I'll update this article as appropriate.

Questions of power

ATI's documents mention a 500W minimum supply, and although we can see why they'd say that, we'll also debunk it in due course. Of course, you definitely want a solid, well-reviewed and well-tested supply for Crossfire and SLI, but 500W is too high. I'll explain later.

Questions unanswered

There's a whole bunch of stuff yet to be answered that ATI don't cater for in the press docs handed out to hacks like me. I'll cover those both in my Computex coverage and my coverage of the actual hardware, when it all arrives. Stay tuned for that in the coming weeks. Hopefully this article should explain Supertiling, Super AA (urgh!) and the basics on what hardware you'll need. It should also give you plenty to talk about in the HEXUS.community with things like almost universal game support (which SLI doesn't have) and Super AA hot topics for you to pick over.

Computex starts today, so there'll be a barrage of extra Crossfire information to be had in the next week or so. Watch our special Computex channel on the main site for more information, where I'll be sniffing out the information, along with Nick and PD, on Crossfire and everything else exciting at Taiwan's premiere trade exhibition for information technology.

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