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- Date:
- Tuesday , June 13, 2006
- Author:
- Brent Justice
- Google +1
BFGTech GeForce 7950 GX2
Is BFG’s new GeForce 7950 GX2 the fastest single video card on the planet? [H] Enthusiast uses real-world gaming and massive 24” & 30” displays to show you what the GX2 is really all about. Canned benchmarks and smaller displays do not tell you the real 7950 story.
NVIDIA GeForce 7950 GX2
NVIDIA is announcing “the world’s fastest single video card” which uses two GPUs to achieve the best performance.
As we mentioned on the previous page the GeForce 7950 GX2 is a single video card with two GPUs on board. This isn’t your typical single video card however. There are actually two separate printed circuit boards (PCBs) connected to this “single” card. The design is quite unique and innovative. Each PCB contains one GPU and the PCBs are connected in an SLI fashion with a built in PCI-Express bus.
Each 7950 GPU is nothing more than a G71 (GeForce 7900 GTX GPU). This means it supports exactly the same 3D features as the GeForce 7900 GTX. It has the same number of pixel shader units (24), the same number of vertex units (8), the same number of raster operators (16), the same number of transistors (278 million) and the same manufacturing process (90nm). The difference is that each 7950 GPU has a lower core and memory clock compared to a 7900 GTX. Each 7950 runs at 500 MHz GPU frequency and interfaces with 512MB of GDDR3 on a 256-bit bus at 1.2 GHz. (7900 GTX stock clocks are 650MHz core and 1.6GHz memory.)
NVIDIA sees this video card as being one single video card, despite the fact it has two PCBs and GPUs, and as such you will find that its specifications are frequently quoted combining the specifications of both GPUs. If you look in the specification comparison image above you will see what we mean. NVIDIA doubles the numbers and quotes the card as having 556 million transistors, 16 vertex shaders, 48 pixel shader units, 32 raster operators, 512-bit GDDR3, 1GB of RAM and double the memory bandwidth and fillrate.
It is very important to realize that this is not entirely accurate when looking at the performance of this video card. Yes, technically it has 1GB of RAM if you add it up. However, each GPU only has access to 512MB of framebuffer space just like two video cards in SLI. Technically if you add up the memory interface widths you will get 512-bit, but each GPU only has access to a 256-bit memory bus per GPU just like SLI. Technically the memory bandwidth is 76.8 GB/sec if you add it up but in reality each GPU has access to 1.2 GHz memory which means 38.4 GB/sec for each GPU. The same goes for the pixel shader units, vertex units, ROPs and everything else they are doubling. Now, since this card does run in a multiple GPU fashion theoretically if you were getting 100% gains from both GPUs in a game then you could say as a whole this card has 76.8 GB/sec of bandwidth. You just need to realize that this is as a whole and each GPU has its own specifications.
Power
Power is an important component to note about the GeForce 7950 GX2. In the past putting two GPUs on a single PCB have resulted in the need for a lot of external power. The GeForce 7950 GX2 is a power and heat friendly video card and this results from NVIDIA re-designing the layout so that it is operating on two PCBs, with new power circuitry and a reduction in clock speeds for each GPU. NVIDIA claims that the GeForce 7950 GX2 will demand less power than a single ATI Radeon X1900 XTX and it will be much less offensive to the ears as well.
The minimum power supply requirement specified by NVIDIA is 400 watts with 27A on the 12v rail. The peak power draw reported by NVIDIA is 143 watts from this video card. That is less power than two GeForce 7900 GTX cards in SLI but more than a single 7900 GTX.
Operation
Above is a diagram that shows the logical interconnects of two GeForce 7950 GX2s. The top green box represents one 7950 GX2 video card and the bottom represents a second 7950 GX2 video card. This shows how the communication would work with two 7950 GX2’s in SLI for Quad GPU.
The most important hardware feature of the GeForce 7950 GX2 is the built in PCI-Express chip on every GeForce 7950 GX2 video card. NVIDIA completely designed in-house their own PCI-Express controller that provides more PCI-Express lanes for each card. The primary benefit of this PCI-Express controller is so that the GeForce 7950 GX2 can be used with literally any motherboard on any motherboard chipset. All that is needed is 1 x16 PCI-Express slot and a system BIOS update. This gives the GeForce 7950 GX2 incredible flexibility. You are not bound by needing an nForce4 SLI chipset to use this card. You can freely put it in any Intel, ATI, VIA, or SiS chipset based motherboard and it will work utilizing both GPUs on the card. However, Quad SLI will of course need an SLI motherboard.
NVIDIA did however run into some compatibility issues getting the GeForce 7950 GX2 working correctly with many motherboards. It seems that they were running into some issues concerning the fact that they are using their own PCI-Express controller and motherboards were not able to identify it and interface with it. Luckily all that is needed to overcome this problem is a system BIOS update according to NVIDIA. NVIDIA currently has an growing list of motherboards and what BIOS versions you need if you want to run a single GeForce 7950 GX2. So check the site out and update your system BIOS or else you won’t be able to use this new video card. Otherwise when it comes to motherboard BIOS, we suggest you prescribe to the, “If it ain’t broke, don’t fix it,” mentality.
Retail Pricing
NVIDIA expects for you to find this card between $599-$649 on the street.