Intel claims that despite larger cache sizes and faster clock speeds, the
Core i7 will actually give greater performance per watt than their previous
quad-core processors. PCSTATS, of course, had to put this to the test.
As always, before any power measurements are taken the CPU power saving and clock speed throttling technologies like Cool 'n'
Quiet, EIST (speedstep) and C1E power states are disabled. PCSTATS then set
about stressing each core of the processor one by one, until all cores were
loaded. For this we used Stress
Prime (SP2004). The total system power consumption, measured in Watts, is
monitored with an Extech Power Analyzer Datalogger (model 380803). T he power
meter is located between the main 120AC supply and the PC's power supply so it
measures the entire computer system, the difference between CPU loaded and
unloaded states is the key value to pay attention to.
The Core i7 920 is already holding up quite well against its closest
competition, the AMD Phenom II X4 955 Black Edition. Intel has managed to get
their fastest quad-core processors to draw less power than their single-core
processors from only a few years ago.
To simulate different CPU usage scenarios, we stressed
the Core i7's four physical cores one by one, and then enabled
HyperThreading and moved up to an eight-core load. Even with double
the amount of threads running, the Core i7 920 is more efficient than the Phenom
II X4 955 Black edition, and is still more efficient than the single-core Pentium
4 540 processor. Intel has made huge inroads with its focus on power efficiency.