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- Date:
- Monday , May 05, 2008
- Author:
- Brent Justice
- Editor:
- Kyle Bennett
- Google +1
9800 GTX vs. SLI vs. 3-way SLI. vs. Quad SLI
How does a 9800 GTX compare to SLI, 3-way SLI, and Quad SLI? We have completed an SLI scaling evaluation using our real world gameplay techniques as well as apples-to-apples testing to see what SLI, 3-way SLI, and Quad SLI can do to improve your gameplay experience.
Introduction
A few weeks ago we did a complete evaluation of GeForce 9800 GTX SLI performance compared to the competition. Overall we found GeForce 9800 GTX SLI to provide positive results in gameplay, allowing high in-game settings at high resolutions. However, using two GeForce 9800 GTX video cards isn’t the limit at all of their capabilities. The GeForce 9800 GTX also supports 3-way SLI. The name says it all; 3-way SLI utilizes three GeForce 9800 GTX video cards to improve gameplay performance.
To summarize the GeForce 9800 GTX, it is a 65nm GPU consisting of 128 stream processors clocked at 1.688MHz with a 675MHz core clock and 512MB of GDDR3 clocked at 2.2GHz.
In this evaluation we are going to utilize three GeForce 9800 GTX video cards, as well as two GeForce 9800 GX2 video cards. All video cards are running at NVIDIA suggested clock speeds. Remember, each GPU on the GeForce 9800 GX2 actually runs at lower clock speeds than the GeForce 9800 GTX. Each GPU on the GeForce 9800 GX2 runs at 600MHz core (vs. 675MHz on the 9800 GTX) and 1.5GHz stream processors (vs. 1.688GHz on the 9800 GTX) and 2GHz memory (vs. 2.2GHz on the 9800 GTX.)
With these video cards we are able to compare GeForce 9800 GTX to GeForce 9800 GTX SLI to GeForce 9800 GTX 3-way SLI to GeForce 9800 GX2 Quad SLI. That is single-GPU, to dual-GPU, to triple-GPU, to Quad-GPU. We are also going to overclock our Intel Core 2 Extreme QX9650 3GHz CPU to 3.66GHz to reduce CPU limitations should there be any.
Setting up SLI
Configuring an SLI system couldn’t be any easier these days. We are using an NVIDIA 790i Ultra SLI motherboard for testing, which has three PCI-Express slots for 3-way SLI using PCIe Gen 2.0. It also supports two GeForce 9800 GX2 video cards for Quad SLI.
SLI
GeForce 9800 GTX SLI is pictured above. We have two GeForce 9800 GTX video cards in the appropriate PCIe slots with a single SLI bridge connector atop the video cards. In this configuration four 6-pin auxiliary power connectors are required. Also, in this configuration there is a wide space between the video cards which lets air move easily between them.
3-way SLI
3-way SLI only requires that we install one more GeForce 9800 GTX in the middle. Now, when we do this we have to use a special 3-way SLI bridge connector. This bridge connects to both SLI finger connectors that are on each video card. 3-way SLI will not work with a single SLI connector; it must connect to every SLI connection on each video card. Most 790i Ultra SLI motherboards should come with this bridge as ours did.
The other factor that is required is to have two more 6-pin auxiliary power connectors available, this means six total power connectors. Now, if your power supply does not have enough power connectors you can use two Molex to PCIe adapters to provide the connections. This is what we have done with our power supply, which only has four auxiliary power connectors total. We had no trouble using the Molex to PCIe converter cables for this setup. Our power supply is rated at 900W and it allowed sufficient power to each video card, even with our CPU overclocked to 3.66GHz.
As you can see, one issue with 3-way SLI is the restriction of airflow with each video card right next to each other. These video cards do get quite hot during operation and you will want to make sure your case is exhausted well.
Quad SLI
Using two GeForce 9800 GX2 video cards we can setup GeForce 9800 GX2 Quad SLI. In this configuration only one SLI bridge connector is required since each video card contains two GPUs each that are hardwired together already. For this setup you need two 8-pin auxiliary power connectors and two 6-pin power connectors.
Enabling SLI
After you have setup the hardware properly you are then ready to install the driver. We are using the latest beta driver at the time of evaluation which is ForceWare 175.12. Once the driver is installed you do have to manually enable SLI, it was not enabled by default for SLI, 3-way SLI, or Quad SLI. Unfortunately multiple-displays are still not supported when SLI is enabled in any configuration. Enabling SLI, 3-way SLI or Quad SLI will only allow you to output to one display.
We can confirm that SLI is enabled and working thanks to NVIDIA’s SLI Indicators. You will notice for SLI (two video cards) it says “SLI” and for 3-way SLI (three video cards) it says “SLI x3” and for Quad SLI (four GPUs) it says “Quad SLI.” This is a very nice feature that lets you know you are getting what you paid for.