Well, we have tested 23 contemporary and not very contemporary graphics accelerators trying to find out their power consumption levels in different operational modes. As we have expected, the best results were demonstrated by Radeon HD 5000 solutions in all categories. And in fact there is nothing surprising about it: they use the most advanced consumer graphics processors available today. The new 40 nm Nvidia solutions represented by GeForce GT 240, 220 and 210 follow closely behind the junior ATI offering from this family, but the top models in the lineup are still unrivalled in this respect and won’t be until GeForce 400 products come out. Since this new family promises to be pretty power-hungry and since G200b based solutions will then move over to GeForce 3000 family, Nvidia may remain an energy-efficiency outsider for quite some time.
From the consumer prospective the best-balanced solution would be ATI Radeon HD 5850 – it is pretty energy-efficient in 2D mode and offers high gaming performance consuming a little over 120 W. its only drawback is its high price – not everyone can spare over $300 for just a graphics card. The second favorite would be Radeon HD 5770 – it is definitely not a gaming solution, but will be ideal for a quiet and economical HTPC system, because it consumes only 13 W during high definition video playback, which would be the primary operational mode for this type of systems. Yes, theoretically, GeForce GT 220 could be an alternative to it, but it has no proper support of high definition audio formats. I have to admit that Radeon HD 5830 spoils the overall positive feel from the Radeon HD 5000 family, because in almost all modes it consumes a little more than Radeon HD 5850, and in games can even yield to Radeon HD 4890.
As for Nvidia solutions, if for some reason you absolutely have to pick one of those, then GeForce GTX 275 is worth taking into consideration, because it elder brother costs more and the younger one doesn’t run as fast in 3D applications. In this case, however, you will have to forget about energy-efficiency as well as about fully-fledged HD video support. However, we only imply the absence of proper hardware VC-1 decoding, which will hardly become a big issue if you have a powerful CPU in your system. If you are fond of games supporting PhysX effects, then it would be nice to bundle your GeForce GTX 275 with a GeForce GT 220, which will function as a discrete PPU.
As for the PSU choice, we have every right to say the following: you will only need a really powerful PSU if you intend to equip your gaming platform with solutions like Radeon HD 5970, GeForce GTX 295 and soon also GeForce GTX 400. Under maximum load the current in some of these graphics cards’ lines may hit 17 A, which is a pretty serious number that is why you must be very careful about the PSU choice. Less monstrous solutions like Radeon HF 5870 have lower energy appetite and should be happy with a quality PSU with 600-650 W capacity. This correlates nicely with our previous conclusions about the total system power consumption levels, which indicated that even a powerful gaming platform could easily fit into a 500 W range. It wouldn’t hurt, however, to have a little extra power available, just in case. Mainstream gaming systems equipped with solutions like Radeon HD 5770 will easily do with a 400 W PSU, just make sure that the power supply unit you pick is reliable and provides stable output voltages: it has never hurt anyone to be a little more cautious, so why risk your entire system by buying a cheap PSU?
Our overclocking experiments showed that power consumption increases significantly only when you raise the GPU voltage, which is a risky undertaking anyway. Without any extreme measures the difference between the startup frequencies and maximum frequencies during overclocking without any vGPU increase was only 20 W for Radeon HD 5850 and 31 W for GeForce GTX 275. I have to say that in the former case some power-saving functions may be disabled during overclocking, namely, the card won’t lower the GPU and memory frequencies in 2D mode and during video playback. Moreover, I have to repeat one more time that overclocking rarely makes a really big difference: if the performance was high enough in nominal mode it will stay the same also during overclocking and the other way around. In other words, overclocking is merely a sport that does have it fair share of excitement and impressiveness, but hardly makes a lot of purely practical sense, especially its extreme variations, which include high risk of overclocked components’ untimely “death”.