To merely test power consumption is not enough any more. While the i7 is the fastest CPU it inherited some of the P4 features. Although Hyperthreading is not a bad thing, the turbo mode maybe questionable, the i7 like it's P4 brother gets hot, really hot. This also results in a much higher power-consumption. So we measured power-consumption with CineBench and FarCry2 too and set them in perspective with the results. Please note our results are peak values but that's ok for comparison purposes.
Let's look how FarCry 2 does:
While the i7 is the fastest CPU it does need about 50% more power compared to a Q9650. If you check the efficiency you see that the Q9 series has the best performance/consumption ratio. Intel claimed any 2% performance improvement does only cost 1% more power-consumption, but we clearly see they failed.
AMD on the other hand has the same problem as Intel, it does consume huge amounts of power, but with the right software-optimization they can keep up with Intel Core2 CPUs. Sadly besides x264 we have not seen much in that area. But while AMD is not just that fast, it's Phenom II X4 CPUs are much cheaper, the 920 sells for under €160,- which can be considered as bargain, while the cheapest Q9300 sells for about €185,-. We hope the recently announced 65W CPUs will give Intel more competition.
We think the Q9 series is the best CPU you can buy, you don't even need to change your memory and still save money on the board. Besides, DDR2 memory is still cheaper, because the 1.65V DDR3 kits have a price-premium and you don't need massive cooling for the CPU. Only professionals where time is essence can profit from the faster i7, but even hardcore gamers can leave it alone. The Q9650 is available for about €285,- and works at 3GHz while the cheapest Nahalem Core i7 920 at 2.66GHz costs under €250,-. A Q9650 is much easier to overclock and you have not to calculate any internal clocks and memory overclocking also works much better.
Also our review proves that, a decent power supply is enough to fit anybody's needs. As long as you don't care about Crossfire or SLI a small power-supply will fit. PC Power & Cooling Silencer 500W does the perfect job and is enough to power all of these nineteen systems, of course not at once. Sadly the companies are into making PSUs bigger and bigger, there is no company out providing a decent 250W and 300W PSU with good efficiency and most "entry" models don't have sufficient connectors such as an often needed EPS12V CPU power connector.
So, long story short, the winner is Core 2 Quad Q9650.