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Monday, June 05, 2006

NVIDIA's GeForce 7950 GX2 graphics card

Techreport Conclusions

Somehow, I didn't really expect a "single" GeForce 7950 GX2 card to be a compelling product outside of a Quad SLI configuration. This puppy does have its warts, including the need for mobo BIOS updates and the SLI-like limitations for multi-monitor use that may turn some power users away. Still, the GX2 is remarkably tame overall. This card takes up no more space, draws no more power, and generates no more heat or noise than a Radeon X1900 XTX, but its performance is in another class altogether. The multi-GPU mojo generally happens transparently, too, thanks to a healthy collection of SLI profiles already established in NVIDIA's drivers. Putting two GPUs on a card has allowed NVIDIA to overcome the limitations of its present GPU designs and of current fab process tech to achieve new performance heights in a single PCI Express slot.

Of course, such things have been possible for quite some time in the form of a two-slot SLI or CrossFire solution, but the GX2 still has much to recommend it. Doubling up on GeForce 7900 GTs would get you an SLI setup in the same price range, but with lower (stock) GPU clock speeds and only 256MB of memory per GPU. And the GX2 works in any chipset, which may prove to be a real boon if you fancy one of Intel's Conroe processors, an Intel chipset, and uber-fast graphics. I could see that combination becoming very popular this summer, if things shake out as expected.

All that's left now is for NVIDIA to enable—and support—Quad SLI in consumer-built systems. Let's hope NVIDIA comes to its senses on that one sooner rather than later.


Nvidia is releasing a graphics card package where two G71 GPUs are already sandwiched together in a single package: its new, top-of-the-line GeForce 7950 GX2.

To call this a single "card" may be a bit of a stretch: Indeed, it only plugs into one PCI Express slot, but physically, the 7950 GX2 is still two cards mounted together, so it still consumes two cards' worth of volume inside the PC chassis. Still, think of it as an SLI option that's already configured for you - that's essentially as easy to install as a single card.

In some regards, it's like having two G71s (7900 GTX), but Nvidia has had to do some tweaking in order for both to work together within this form factor. Nevertheless, you're getting the benefits of 1 GB of GDDR3 memory (512 MB per GPU), plus a total of 48 pixel pipes and 16 vertex shaders, again divided among the two GPUs. But core clock speed is reduced a bit, from the 7900's 650 MHz to 500 MHz, with memory clock speed at 600 MHz. Yet the presence of two processors manages to boost total memory bandwidth from the 7900's 51.2 GB/sec to a formidable 78.6 GB/sec.

Nvidia warns this morning that the 7950 "will not be faster than two GeForce 7900 GTX-based graphics cards in an SLI configuration, because the clock speeds on the GeForce 7950 GPU are lower than the GeForce 7900 GTX." The company has not stated whether this is due to space and cooling constraints, or the need to maintain the viability of the dual-7900 option. But it is promising the paired card will be able to drive a new generation of widescreen, flat-panel displays at 2560 x 1600 resolution, using "dual dual link DVI" (two dual-link sockets), effectively pumping out the content of four DVI channels simultaneously.

UPDATE: In Darren Polkowski's latest round of tests for Tom's Hardware Guide, he concluded the 7950 GX2 is a solid performer, that he feels is "worth the $650 that one would have to shell out for extreme graphics capability." The minimum 53% boost in memory bandwidth is quite welcome, but Darren's also pleased with the card's reasonable use of space, without capacitors sticking out and bumping into things, while leaving enough room in the substrate sandwich to leave the #2 card in the pair reasonably cool.

Also, as TG Daily discovered this afternoon, the first GX2 cards to hit the streets are selling for just under $600, with higher-clocked models selling for as high as $775.

If you're already pairing two or more 7950 GX2s together in your mind, be advised, Nvidia isn't making this dream a reality for consumers just yet. For you to pair GX2s in a quad-SLI setting, you need to have an nForce 4 SLI or nForce 590/570 SLI motherboard, plus a little logo saying you're an authorized Nvidia system builder.

The new card-and-a-half also marks the debut of Nvidia's ForceWare Release 90 driver, which now features an optional control panel that the company describes as "Vista-inspired," with more descriptive icons for the novice user.

The idea of packing two graphics processors isn't new. Ignoring Nvidia's reference design, Gigabyte unveiled its dual GPU design based on 6600 GT processors in February of last year, followed by a version that used regular 6600 processors in March and 6800 GT variant that arrived in May of last year.


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