The rumors were true. Nvidia confirmed on its blog this morning that SLI support is finally coming to motherboards with AMD chipsets. That's been a long time coming, since Intel users have been enjoying licensed SLI multi-GPU capabilities since the release of the first Core i7 processors and accompanying X58 chipsets back in late 2008.
According to Nvidia, SLI support will make its way into future motherboards with AMD 990FX, 990X, and 970 chipsets. The first board manufacturers to hop on that bandwagon will be Asus, ASRock, Gigabyte, and MSI, though more will purportedly follow. I don't believe AMD has actually announced those three chipsets yet, but word from the rumor mill suggests they will accompany Bulldozer-based Zambezi processors—the chipmaker's next flagship CPU family.
Nvidia's blog post provides a rather interesting justification for its change of heart regarding SLI licensing for AMD chipsets. Listen to this:
Long term gamers probably remember that for a long time AMD offered great high-end CPUs, but in recent years, AMD's stature as the preferred gaming CPU fell by the wayside and Intel CPUs have been the gamers' choice. For this reason, we've only licensed SLI for motherboards with Intel chipsets. However, we've been recently hearing chants of "SLI for AMD CPUs", and figured that now is a great time to do it. After all, we want to make sure gamers can benefit from the new CPU competitive landscape and ensure they have NVIDIA SLI.
This explanation might have made sense if SLI support had been strictly reserved to top-of-the-line Intel platforms without competition from AMD. Except that hasn't been the case. Plenty of P55 motherboards shipped with SLI support, and matching LGA1156 Intel processors had worthy competitors from the Phenom II camp at most price points. Not only that, but PC games just don't require much CPU horsepower these days, so artificially tying SLI to high-end CPU platforms wouldn't much make sense.
There's one thing Nvidia isn't mentioning, and that's the fact that AMD's Phenom II processors could (and still can) be coupled with SLI-capable mobos powered by Nvidia's own nForce chipsets. Some of those boards are still available today. That's because, unlike Intel, AMD never used licensing trickery to block Nvidia from competing with its homebrewed chipsets.
More likely than not, I would guess Nvidia simply didn't want to cannibalize sales from the last remnants of its nForce business. Perhaps that strategy will only change with Zambezi processors because Nvidia has no next-gen nForce chipsets in the pipeline, having halted chipset development in October 2009.