NVISION — If you want to combine a pair of GeForce graphics cards with a new Core i7 processor from Intel later this year, you're in luck. Just after the grand finale for its Nvision conference, Nvidia gathered reporters to inform them of a somewhat surprising and apparently very recent decision: the firm plans to enable its SLI multi-GPU scheme to work with Intel's X58 chipset—without the need for an nForce 200 PCI Express bridge chip on the motherboard.
The fate of SLI support on the X58 chipset—intended for Core i7 processors, which are code-named "Nehalem"—has been a question mark for some time now. Nvidia has said that it won't be making chipsets that work with the Core i7's QuickPath Interconnect (QPI), and it had instead proposed that motherboard makers use its nForce 200 chip on their boards. The presence of that bit of Nvidia hardware would then make the mobo kosher for SLI support. However, the company said today that it realized such a silicon solution would limit SLI to a small number of very high end motherboards, effectively roping off SLI from the mainstream of the enthusiast PC market. Rather than be forced into that situation, Nvidia has elected to allow SLI on the X58 chipset—under certain circumstances.
Motherboard makers who wish to have their X58 boards certified for SLI will have to submit their products for testing in Nvidia's Santa Clara certification lab, and those boards must pass basic testing for functionality, slot placement, and the like. Certification will not be free, either. Board makers will have to select from a menu of licensing options available to them. Certified boards will also be required to display an "SLI Certified" logo on their boxes and other marketing materials.
Once a board is certified, Nvidia will provide the board maker with an approval key (called a "cookie") that it must embed in the system BIOS. The combination of this approval key and an X58 chipset will then unlock SLI support in Nvidia's ForceWare driver software. Nvidia acknowledged to us up front that users would more than likely hack the BIOSes of non-certified X58 boards and add "cookies" to them, but said it won't get in the way of such things. The certification program is intended for motherboard and PC makers, and end-users' actions don't appear to be a big source of concern.
X58 SLI will come in a variety of flavors, since the firm will support a fairly broad array of PCI Express lane configurations for PCIe graphics slots on motherboards, including everything from dual x16 to quad x8 lanes of Gen2 PCIe connectivity. (Yep, it looks like we may see quad SLI in four cards make its debut with the Core i7.) The nForce 200 will still get a piece of the action, too—configs with four true 16-lane PCIe slots via dual nForce 200 chips will of course be supported. X58 boards with nForce 200 chips are likely already deep into the development process by now, or we likely wouldn't see many of these, I suspect.
Why the change in direction? Nvidia says its reasoning in part was simply that without a QuickPath Interconnect (QPI) chipset of its own, the market for Core i7 motherboards would be difficult for it to attack. In other words, Intel seems to have forced Nvidia's hand here by blocking off access to its QuickPath Interconnect. Forced to choose between opening up SLI to work on Intel chipsets or losing out on GPU sales, the firm chose something of a middle way in which it retains control over SLI certification and reaps some royalty fees but still brings SLI to Intel's enthusiast-class PC platform. Intel is even welcome to submit its own X58 motherboards for SLI certification, Nvidia spokesman Tom Petersen said, although not all board makers will be offered the same set of licensing options at the same price.
Petersen also told us Intel wasn't a party to Nvidia's decision to allow SLI on the X58, so there's no apparent quid pro quo here.
Nvidia does not plan to abandon its chipset business entirely and will continue to make core-logic products for other Intel platforms, like the current Core 2 one. In fact, Petersen noted that Nvidia will soon be making an announcement related to integrated graphics chipsets for Intel processors. That's a big change for Nvidia; the company hasn't yet challenged Intel's higher-volume chipsets in the mainstream PC market, despite the fact that Intel's integrated graphics solutions are generally considered to be rather weak.
Unfortunately, Nvidia still seems committed to maintaining the fiction that locking its competitors' chipsets out of SLI was (and still is) driven by technological barriers rather than business reasons. When asked why the company had decided to open up SLI on the X58, Petersen claimed SLI had previously relied on two functions specific to nForce chipsets, PW Shortcut and broadcast. Now, however, PCIe Gen 2 has made peer-to-peer writes a standard feature, eliminating the need for PW Shortcut. Nvidia's driver team, he said, is modifying its driver to handle the broadcast function in software. That explanation would seem to make perfect sense, yet one can't help but note that SLI support is not forthcoming for AMD's PCIe Gen2-capable chipsets or for Intel's Core 2 chipsets. Business concerns are the in driver's seat here, not technical hurdles.
Regardless of its justification, though, this development is undoubtedly a welcome one for PC enthusiasts, who should be able to select from a number of Core i7 motherboards that support not only CrossFire but SLI, as well, later this year.