NVIDIA revisits dual-GPU graphics boards

NVIDIA has classed up their card line up with a new product that is both powerful for gaming and easy on the eyes with a unique completely enclosed cooling design. You might want to keep that credit card with your better half though before heading in to read.

We can remember first “officially” seeing the GeForce 9800 GX2 back in January when another website featured a few high resolution images of it.  It definitely didn’t LOOK like any other graphics card on the market at the time, with its fully enclosed cooling design and oddly stacked DVI outputs.  We got another “clue” when NVIDIA itself mentioned the 9800 GX2 in a press FAQ about the launch of AMD’s Radeon HD 3870 X2 card.

Just like the HD 3870 X2, the new NVIDIA GeForce 9800 GX2 is a dual-GPU graphics board with only a single connection to the motherboard via PCI Express.  The common way of describing these cards is “SLI on a card” or “CrossFire on a card” depending on your party affiliation.  These descriptions are about as accurate as you can get in ten words or less, though as we’ll see the NVIDIA 9800 GX2 is even more like “SLI on a card” than its AMD competition.

What really matters is performance in games; and after a quick overview of technology behind the new NVIDIA GeForce 9800 GX2 we’ll dive deep into that all important aspect.

The 9800 GX2 Graphics Card

In another parallel between the 9800 GX2 and the HD 3870 X2, NVIDIA’s new card is really nothing new when it comes to the chip architecture.  The card is built around a pair of G92-based 8800 GTS 512MB GPUs that run at different clock speeds but operate in SLI mode when enabled in the NVIDIA control panel for improved gaming performance.  How much gain depends on the game you want to play.

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The specifications for the 9800 GX2 pretty much speak for themselves and follow the trends we are used to seeing with dual-GPU graphics cards: pair a couple of current-generation GPUs on a single card, lower the clocks to stay inside a reasonable thermal envelope; cycle, rinse, repeat.  Where as the single GPU 8800 GTS 512MB card runs at 650 MHz core clock with 128 shader units running at 1625 MHz, the new 9800 GX2 sports twice the stream processors running at 1500 MHz and a core clock rate of 600 MHz.  It just happens that these clock rates are the same as those found on the G92-based 8800 GT though it only has 112 stream processors. 

For memory support the 9800 GX2 has a very slightly increased memory speed of 1000 MHz and 1GB of total frame buffer, 512MB of which is dedicated to each GPU.  The board consumes a decently high amount of power, rated at 197 watts according to NVIDIA here, and requires both an 8-pin power connector and a 6-pin power connector from your power supply.  Some vendors will be including adapters for 6-pin to 8-pin connections, but NVIDIA isn’t guaranteeing that will work – your power supply needs to be able to push out at least 12A on each 12V rail. 

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While the card is definitely nice to look at, that MSRP range definitely hurts.  Since the AMD Radeon HD 3870 X2 can be found for $419 and under, the GeForce 9800 GX2 has to perform to justify that price tag.

You can see also that the 9800 GX2 will feature the same dual dual-link DVI ports that have graced most GPUs for a couple years but there is also an integrated HDMI port on the card as well that will allow for audio pass through.  We’ll show that on the following pages with a more detailed look at the retail cards.

Besides the added benefits of having two GPUs on the 9800 GX2, it is also the second graphics card in the 9000-series (the GeForce 9600 GT was the first) and that means some features that involve words like “hybrid” in them are going to be found on it.

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Now, if you have a GeForce 9800 GX2 in your system, chances are Hybrid SLI, pairing your discrete and on-board GPUs (when they are actually available) probably isn’t what you are going to be interested in.  However, an interesting feature that NVIDIA is talking about but not showing yet is the ability for the mGPU and dGPU to work together in HybridPower mode.  Basically, this would allow the discrete graphics card (or cards) to completely power down when you are not gaming and you have a compatible NVIDIA nForce chipset with integrated graphics.  Using the SMBus, NVIDIA is saying that this can lead to significant power savings.

Another interesting feature I am sure most of you expect with the GeForce 9800 GX2 is renewed support for Quad SLI:

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In the good old days (um not really good for those that bought it) NVIDIA achieved Quad SLI by doing “AFR of SFR” which basically took two pairs of GPUs, set them to do split frame rendering and then alternated those frames.  With late DX9 and DX10 titles, SFR is really no longer an option as even AFR is getting more difficult to work with, so the idea of “AFR of SFR” was canned. 

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NVIDIA’s new Quad SLI technology uses 4-way SFR in the same fashion that our first 3-way SLI tests used 3-way SFR.  Quad SLI technology isn’t being shown today though as NVIDIA has placed a separate NDA on that event.

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