4 - Power Consumption

Power Consumption

Already mentioned in the last chapter, yet the GTX 260 has a 182W TDP. Which boils down the peak wattage (not continuous or average which is lower), for a product of this caliber it's really not that bad. More transistors means more power consumption ... well you figured that out yourself already I guess. The new GPU however is one of the most energy aware products you'll find on the market today. NVIDIA made sure several new power states are active in the GPU. What this means is that depending on the task at hand you assign to the GPU, it'll react to that in terms of power consumption. NVIDIA's integrated these 'p-states' and allows the GPU to alter clocks, voltages and frequencies on the fly. Very interesting is that certain parts of the GPU when not used, can be shut down, preserving energy. In GPU terminology this is called clock-gating circuitry, it effectively "shuts down" blocks of the GPU which are not being used at a particular time, reducing power during periods of non-peak GPU utilization.

For example .. in idle this graphics processor only consumes 25 watts. I think the previous generation products consumed up-to 70 watts alone in idle. Another nice example is that movie playback is accelerated and enhanced over the GPU (Purevideo), when you decode 1080P content (Blu-ray) movies you'd figure that it would use up a lot of power, right ? Think again. Remember what I said about the GPU being able to shutdown segments of the GPU? Likely (and I'm not 100% sure here) mainly the video processor, IO and perhaps one shader block for some post-processing are at work. While decoding a 1080P movie over the GPU this product utilizes only 35 Watts. That's pretty amazing to be honest. Let's take an overview on what we just said:

• Idle/2D power mode: approx. 25W
• Blu-ray DVD playback mode: approx. 35W
• Full 3D performance mode: varies - worst case TDP 236W for GTX 280
• Full 3D performance mode: varies - worst case TDP 182W for GTX 260
• HybridPower mode: effectively 0W

Using a HybridPower-capable nForce motherboard a GeForce GTX 200 GPU can be fully powered off when not performing intensive graphics operations and graphics output can be handled by the motherboard's IGP.

So though the processor can peak towards 182 Watt with hefty gaming, the reality is that it's just as much as a GeForce 8800 Ultra, yet you have double the performance and the overall picture of this GPU in more common situations seems to be very energy efficient.

We'll now show you some tests we have done on overall power consumption of the PC. Looking at it from a performance versus wattage point of view, the power consumption is not as bad as I expected it to be. The card according to NVIDIA has a TDP of roughly 182 Watts.

The methodology is simple: We have a device constantly monitoring the power draw from the PC. After we have run all our tests and benchmarks we look at the recorded maximum peak; and that's the bulls-eye you need to observe as the power peak is extremely important. Bare in mind that you are not looking at the power consumption of the graphics card, but the consumption of the entire PC.

Our test system contains a Core 2 Duo X6800 Extreme Processor, the nForce 680i mainboard, a passive water-cooling solution on the CPU, DVD-rom and a WD Raptor drive. The results:

• PC in Idle = 159 Watt
• PC 100% usage (wattage gaming Peak) = 302 Watt

The monitoring device is reporting a maximum system wattage peak at roughly 302 Watts, and for a PC with this high-end card, that is not excessive at all.

Recommended Power Supply

So here's my power supply recommendation:

GeForce GTX 260 | 280

• A GeForce GTX 260 requires you to have a 500 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 38 Amps available on the 12 volts rails.
• A GeForce GTX 280 requires you to have a 550 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 40 Amps available on the 12 volts rails.

GeForce GTX 260 | 280 SLI

• A second GeForce GTX 260 requires you to have a 700 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 50 Amps available on the 12 volts rails.
• A second GeForce GTX 280 requires you to have a 800 Watt power supply unit at minimum if you use it in a high-end system. That power supply needs to have (in total accumulated) at least 55 Amps available on the 12 volts rails.
• 3-way SLI ...  well check our article on Wednesday please.

There are many good PSU's out there, please do have a look at our many PSU reviews as we have loads of recommended PSU's for you to check out in there. What would happen if your PSU can't cope with the load?:

• bad 3D performance
• crashing games
• spontaneous reset or imminent shutdown of the  PC
• freezes during gameplay
• PSU overload can cause it to break down