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GeForce 7950 GX2 Hands-On Preview
June 05, 2006

Summary: Quad SLI technology is almost here, and Brandon whips up some benchmarks of the GeForce 7950 GX2 in this preview. Results from F.E.A.R., Half-Life 2: Lost Coast, Oblivion, Quake 4 and more lie within.


IntroductionPage:: ( 1 / 12 )

Over time Gigabyte and motherboard manufacturers ASUS and MSI released follow-on single-PCB (printed circuit board) SLI combo cards based on more powerful GPUs like the GeForce 6800 GT and GeForce 7800 GT. These cards delivered even more performance for gamers, with the only caveat being that you couldn’t combine two of these specialized cards to deliver up to four times the performance of a single GeForce card.

That’s where NVIDIA’s Quad SLI technology comes in.

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With Quad SLI, two GeForce GPUs and memory are combined on one board, only two of these cards can be combined together for a total of four GPUs in one Quad SLI system. We first took a look at Quad SLI a little over a month ago in our GeForce 7900 GX2 Quad SLI Performance Preview article and found that while the technology worked, it did have its fair share of issues. Stability wasn’t the greatest, we ran into numerous crashes, BSODs and other errors, while its performance wasn’t quite up to the level that was expected when the technology was first announced, even at ultra high-resolutions such as 2048x1536 and 2560x1600.

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Since then NVIDIA’s been working furiously on improving their Quad SLI technology, it’s been discovered that a lot of the stability issues we were running into were caused by the motherboard’s BIOS, while newer drivers have improved NVIDIA’s performance. But NVIDIA didn’t stop there, with today’s release of the GeForce 7950 GX2, NVIDIA is also introducing newer Quad SLI hardware that resolves one of the chief criticisms levied at the original GeForce 7900 GX2 Quad SLI card: its immense size. One GeForce 7900 GX2 measures over one foot in length!

Today’s GeForce 7950 GX2 launch is a little different than the initial GeForce 7900 GX2 Quad SLI launch though in the sense that NVIDIA’s focusing on the 7950 GX2’s performance in a single-card SLI configuration, claiming that the GeForce 7950 GX2 is the “highest performing single graphics board on the market”. Quad SLI support for the GeForce 7950 GX2 isn’t supported by NVIDIA’s latest driver just yet. Let’s take a closer look at what’s new with the card.

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Board analysisPage:: ( 2 / 12 )

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At first glance, the GeForce 7950 GX2 looks like one card with one GPU and one heatsink/fan unit at some angles, particularly when looking at the card from directly above. Tilt the board a few degrees though and you’ll quickly see a second PCB lying underneath the first PCB, complete with its own GPU and heatsink/fan unit, 512MB of memory, as well as the underlying x16 PCI Express graphics interface.

Each heatsink/fan unit is rather slim, a little larger than the reference cooler used on the GeForce 7900 GT basically, being a single-slot design. The two PCBs are then grafted together, so one GeForce 7950 GX2 will take up two slots in your system. The PCI Express graphics slot sitting directly above the card, as well as the slot directly adjacent to your graphics card. This is the same setup NVIDIA used previously on their GeForce 7900 GX2 Quad SLI card.


GeForce 79XX Specifications
GeForce 7950 GX2GeForce 7900 GTXGeForce 7900 GT
Core Clock Speed (Vertex, core)500/500700/650470/450
Memory Speed600MHz800MHz660MHz
Pixel Shaders24x2=482424
Vertex Shaders8x2=1688
ROPs16x2=321616
Memory Interface256-bit per GPU256-bit256-bit
Memory Onboard512MB per GPU 1GB total512MB256MB
Pixel Fill-Rate1610.47.2
Texture Fill-Rate2415.610.8



Since the 7950 GX2 and 7900 GX2 share similar clock speeds, performance between the two boards is the same in a single-card configuration.

Instead of performance, the key difference between the GeForce 7950 GX2 and the GeForce 7900 GX2 lies in the board’s design; weighing in at just 9” long, the GeForce 7950 GX2 is considerably shorter than the GeForce 7900 GX2 board it replaces. This makes the card easier to fit in most cases, not to mention more breathing room for installing other devices such as hard drives. The original GeForce 7900 GX2 board was so long that it could get in the way of these devices.

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But the changes don’t stop there, as NVIDIA has also removed one of the SLI bridge connectors on the GeForce 7950 GX2, as well as one of the 6-pin PCI Express power connectors on the board. Previously the GeForce 7900 GX2 required two 6-pin power connections to run properly, meaning you needed four different power cables to run Quad SLI! This extra cabling takes up even more space in your case, and of course requires you to run additional power cables to your graphics cards.



Board analysis (cont’d)Page:: ( 3 / 12 )

Like previous GeForce 7900 cards, the GeForce 7950 GX2 sports two dual-link DVI connectors.

New cooling

Besides the revised board design, another change NVIDIA’s implemented in the GeForce 7950 GX2 is a new cooling solution. The previous cooler NVIDIA used on the GeForce 7900 GX2 was rather large, and could generate a lot of noise when the board was running under load. The new cooler is considerably smaller and generates less noise than its predecessor, all while keeping the GPU cool.

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One aspect that’s a little deceiving about both the GeForce 7900 GX2 and the GeForce 7950 GX2 is that while the backplate on these cards have vented holes on it, suggesting that hot air from the GPU exhausts out these holes, this actually isn’t the case, the vents on the back of the GeForce GX2 cards are merely decorative, hot air from the card’s cooler doesn’t exit here. The ducted enclosure NVIDIA uses simply isn’t long enough for hot air to escape through, instead the air passes out the top and left side of the card’s cooler.

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Here’s a summary of what’s changed with the GeForce 7950 GX2:

  • Shorter board design: The GeForce 7950 GX2 measures in at just 9”; about the same length as a GeForce 7900 GTX card. As you’ve no doubt seen in our pictures, this is considerably shorter than the GeForce 7900 GX2.
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  • One power connector: Whereas the original GeForce 7900 GX2 had two 6-pin PCI Express power connectors – one per PCB – NVIDIA’s managed to reduce the number of power connectors to just one total. The result is that less cabling is necessary to power the GeForce 7950 GX2 card, so you don’t have to run multiple power cables to one graphics card anymore.
  • One SLI bridge connector: On previous GeForce 7900 GX2 cards, two SLI bridge cables were required to run Quad SLI, for the GeForce 7950 GX2 only one SLI bridge cable is needed. NVIDIA mentions that performance is unchanged from the two-connector approach used on GeForce 7900 GX2.
  • New cooling: The new cooler used on the GeForce 7950 GX2 is smaller and runs quieter than the 7900 GX2 cooler. It seems to do a pretty good job of keeping the GPU cool as well in our opinion.
  • HDCP: The GeForce 7950 GX2 is the first GeForce GPU to ship with cards that feature out-of-the-box support for HDCP. Previously the GPU supported the technology, but the cards didn’t ship with the crypto-ROM chips that were required to store the HDCP keys. As a result HD-DVD and Blu-Ray discs wouldn’t run at full resolution. NVIDIA’s requiring all their board partners to include the crypto-ROM chip on their GeForce 7950 GX2 cards.
  • Same clock speeds: The GeForce 7950 GX2 ships with the exact same GPU as the one used in the older GeForce 7900 GX2 Quad SLI cards. The graphics core on each GPU runs at 500MHz, while the memory runs at 600MHz. That’s 150MHz slower on the graphics core than the GeForce 7900 GTX, and 200MHz slower on the memory, so one GeForce 7950 GX2 card will never match the performance of a fully-fledged dual-GPU GeForce 7900 GTX SLI setup, but with two GPUs onboard each GeForce 7950 GX2 card, it’s more than enough performance to best the performance of a single GeForce 7900 GTX card, particularly at high resolutions. With an upcoming ForceWare driver, you can then combine a second GeForce 7950 GX2 card in the future for Quad SLI support. That’s the plan at least.

    Keep in mind that you’ll still need an nForce SLI motherboard to support SLI with the GeForce 7950 GX2. If you plug a GeForce 7950 GX2 card into an nForce4 Ultra or nForce 570 Ultra motherboard, the card will work, but only one of the GPUs on the board will function. You’ll need to upgrade to an SLI motherboard if you want both GPUs on your GeForce 7950 GX2 card to operate in SLI mode.

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    The motherboard’s BIOS

    One aspect that NVIDIA’s been stressing concerning the use of the GeForce 7900 GX2 and GeForce 7950 GX2 is that it’s critical that your motherboard have a GX2-compliant BIOS installed prior to use for optimal results. The GeForce 7900 GX2 and 7950 GX2 have a special internal 48-lane PCI Express switch that essentially splits one x16 PCI Express signal into three pieces, 32 lanes are split between the two GPUs present on the GX2 board, while the remaining 16 are used for the PCI Express interface. This allows each of the GPU’s on the GeForce 7950 GX2 to operate at full PCI Express bandwidth while physically only using one PCI Express graphics slot, without this switch you’d need an SLI motherboard with four x16 PCI Express graphics slots to perform this. Not to mention that the nForce chipset would need more PCI Express lanes for Quad SLI.

    In any case, the system BIOS of most motherboards is not used to seeing this switch, and while the system may technically work, it may not run with optimal performance and/or stability may be compromised. (This is what we saw with our GeForce 7900 GX2 setup a month ago.) This includes many of the nForce 590 SLI motherboards that were just launched by NVIDIA a few weeks ago. You’ll need to update your motherboard’s BIOS in order to run the GeForce 7950 GX2 card properly. NVIDIA is maintaining a list of GX2-compatible motherboards and the proper minimum BIOS required in order for the technology to work properly at http://www.nvidia.com/gx2, so you’ll want to check this site out if you plan on running a GX2 card in the near future.

    Now that we’ve gone over what’s new with the technology, let’s see how it performs…



    Test SystemsPage:: ( 4 / 12 )

    System Setup


    AMD Athlon 64 FX-62

    ASUS M2N32 Deluxe

    2GB Corsair Twin2X2048-6400C4

    BFG GeForce 7950 GX2
    NVIDIA GeForce 7900 GTX 512MB
    Driver version ForceWare 91.29

    250GB Maxtor Hard Drive Maxline III SATA Hard Drive w/16MB Cache

    Windows XP Professional SP1

    DirectX 9.0c


    Benchmarks

    Half-Life 2 Lost Coast
    Far Cry 1.33
    F.E.A.R. 1.04
    Quake 4 1.2
    Elder Scrolls IV: Oblivion
    3DMark 06

    Notes

    Unfortunately we only had less than 24 hours to test the GeForce 7950 GX2 card before we had to leave for Computex 2006 in Taipei, Taiwan. As a result, we only had enough time to run a handful of games and only three card configurations: the GeForce 7900 GTX, 7900 GTX SLI, and the GeForce 7950. This is far from ideal, as we would have liked to have included more games as well as more cards, including the GeForce 7900 GT running in an SLI configuration as well as the Radeon X1900 XTX. We also didn’t have time to test overclocking extensively. We’ll run all these tests once we get back from Taiwan and post it up as our official review of the BFG card.




    HDR: HL2 Lost CoastPage:: ( 5 / 12 )

    Half-Life 2: Lost Coast – Direct3D








    3DMark 06Page:: ( 6 / 12 )

    3DMark 06 – Direct3D







    Quake 4Page:: ( 7 / 12 )

    Quake 4 – OpenGL









    F.E.A.R. PerformancePage:: ( 8 / 12 )

    F.E.A.R. – Direct3D









    Oblivion Mountains HDRPage:: ( 9 / 12 )

    Oblivion – Direct3D








    Oblivion Foliage HDRPage:: ( 10 / 12 )

    Oblivion – Direct3D









    Far Cry HDRPage:: ( 11 / 12 )

    Far Cry – Direct3D








    ConclusionPage:: ( 12 / 12 )


    This leaves the GeForce 7950 GX2 in an interesting position. For enthusiasts looking for the ultimate in performance, the GeForce 7900 GTX SLI setup clearly delivers significantly more performance. At the same time however one GeForce 7950 GX2 card runs faster than a single GeForce 7900 GTX. To further entice gamers NVIDIA’s pricing the GeForce 7950 GX2 very aggressively, we’ve been told to expect board prices to range from $599-$649. If these prices hold true, this places the GeForce 7950 GX2 at just $100-$150 more than a 7900 GTX. That’s not too bad when you consider the price of buying two GeForce 7900 GTs (which should perform similarly to one GeForce 7950 GX2), or two GeForce 7900 GTX cards, especially considering the added flexibility of going to Quad SLI at some point in the near future, not to mention the board’s built-in support for HDCP. Considering these factors, you could actually argue that the board is somewhat a bargain.

    We still wish it supported Quad SLI though.

    After testing both the GeForce 7900 GX2 and the 7950 GX2, we definitely prefer the latter card. Basically the GeForce 7950 GX2 is a Geforce 7900 GX2 card that’s easier to live with on a day-to-day basis. The card is significantly smaller than its predecessor and it runs quieter. The smaller size makes it easier to install inside your case, especially if your chassis is populated with lots of hard drives, and with fewer power connectors on the board, you don’t need a myriad of power cables to run it all. As far as powering the GeForce 7950 GX2 is concerned, NVIDIA recommends a 400W power supply with 27A on the 12V rail for running a single GeForce 7950 GX2 card, they haven’t provided any info on the power requirements for Quad SLI just yet, but we’ve run our GeForce 7900 GX2 cards on power supplies as low as 520W, so hopefully it won’t be too bad.

    So far our initial impressions of the GeForce 7950 GX2 are pretty positive, but we haven’t had enough time to run the card through our full suite of tests due to our trip to Taiwan for Computex. We’ll have a more detailed review of the BFG card once we get back, by then NVIDIA may have a new driver for the card anyway.

    The closer NVIDIA and their board partners can stick to that $600 price tag the better. With such aggressive pricing the GeForce 7950 GX2 could have some gamers thinking twice about plunking down $480+ for a Radeon X1900 XTX or GeForce 7900 GTX card…

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