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Power Consumption & PSU
When you are more than doubling up your transistor count you can rest assured that such a thing will have an adverse effect on power consumption as well. Below we'll show you some tests we have done on overall power consumption of the PC. Looking it from a performance versus wattage point of view the power consumption is not that bad as I expected it to be.
We had a total wattage peak at 375 Watts for the 8800 GTX XXX edition, which is a lot but not excessive. It's definitely something you need to be aware of. NVIDIA states that the G80 core can peak at 145.5 Watts with 116.6 on average during gameplay.
We tested this on a new Core 2 Duo X6800 Extreme Processor, the nForce 680i mainboard, a passive water-cooling solution on the CPU, DVD-rom and WD Raptor drive. All that in combo with the GeForce 8800 GTX summed up to a peak load of roughly 375 Watts.
So here's my power supply recommendation for today:
The GeForce 8800 GTX requires you to have a 450 Watt power supply unit at minimum if you use it in a high-end system. You'll also notice that the GTX uses two 6-pin power connectors so I'd like to strongly advise a PSU with dual 12-volts rails here to make sure you have two 6-pin connectors.
Why does the GeForce 8800 GTX have two 6-pin power connectors ? Well, the PCI Express spec allows for 75W from the edge connector plus 75W from each external 6-pin power connector. The GeForce 8800 GTX requires two 6-pin power connectors to deliver the full power requirements of the board while adhering to the PCI Express edge connector and 6-pin connector specification. So it's more fitting a specification rather then it was "absolutely" necessity.
More importantly than just staring yourself blind on 450+ Watts .. you need a PSU with a total 30A rating on the 12 Volts rails.
If you have dough to spend and opt the guru path of righteousness by doubling up towards two cards in your system -> SLI then you should end up with a 700 Watt or better PSU with a 40 AMPs 12 Volts rail. And yes I agree this is getting a little out of hand. As stated, we need to start thinking about mother nature a bit more, this increasing trend in power consumption can't continue.
BTW if you tend to overclock with such an SLI setup, then I strongly recommend a KiloWatt PSU. Not that it's needed in the sense of using up a 1000 Watts, but it's because these PSU's have a lot of ampere to spare on the important voltage distribution rails. That results is stability, which is very important while overclocking. We use the Enermax Galaxy 1kW PSU (review here) which allows high over clocks while maintaining stable voltage regulation.
We did test GeForce 8800 GTX in SLI a while ago and as far as power consumption goes it did exceed a 500 Watt peak in a non-overclocked environment. There are some good SLI certified PSU's out there, again 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
Dangerous Liaisons - temperatures of the graphics card
Let's have a look at the temperatures these design coolers produce. We measured at a room temperature of 22 Degrees C.
Fact is that the core temperature of the G80 product in combo with the new design cooler is high. At idle all G80 cards were running at ~69 Degrees C which is considered to be high.
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The peak temperature when the product was utilized at 100% was 82 degrees C. Now if you find this to be high then grab the latest Rivatuner and force the cooling unit to 60% utilization. It's not a lot more noisy yet temps will drop below 65 Degrees.
This is downside of a pre-overclocked product folks, while it's not really an issue, it is much hotter.
Noise Levels coming from the graphics card
When graphics cards produce a lot of heat usually that heat needs to be transported away from the hot core as fast as possible. Often you'll see massive active fan solutions that can indeed get rid of the heat, yet all the fans these days make the PC a noisy son of a gun. I'm doing a little try out today with noise monitoring, so basically the test we do is extremely subjective. We bough a certified dBA meter and will start measuring how many dBA originate from the PC. Why is this subjective you ask? Well, there is always noise in the background, from the streets, from the HD, PSU fan etc etc, so this is by a mile or two not a precise measurement. You could only achieve objective measurement in a sound test chamber.
The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBa level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement.
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We startup a benchmark, we take the dBA meter, move away 75 CM and then aim the device at the active fan on the graphics card. We measure almost 45 dBa on the PC for the XFX 8800, which is to be considered a quiet to moderate noise level coming from the entire PC. While being big the new cooler is doing a very good job. Not bad at all.
