AMD's latest Phenom II CPUs are built on a 45nm
manufacturing process, so we'll see if this, along with the re-architecting of
the Phenom II's microprocessor design will reduce power draw compared to Intel's
CPUs, as well as previous AMD chips.
Wading through the technical numbers to
figure out the differences can be confusing because Intel and AMD report power
values in slightly different ways. On paper AMD lists its processors
maximum power TDP value, while Intel posts typical
Thermal Design Power figures.
Obviously the two measurements of processor power
consumption are not quite directly comparable, so to find out how processors
stack up in the power efficiency department we need to measure how much power
the computer draws while idle, then while in a CPU-stressed state.
To get a more accurate indication of what speeds
the processors are currently running at, PCSTATS first disabled a bunch of AMD
and Intel's power saving and CPU clock speed throttling technologies like Cool
'n' Quiet, EIST (speedstep) and C1E power states.
To simulate single-core load a program called Stress Prime (SP2004) is used.
PCSTATS set about stressing each processor from one to all cores. This programs
gives better insight into different power draw scenarios. The SP2004 program is
multi-threaded, allowing individual CPU cores to be stressed by each instance of
the program. Total system power consumption was read with the Extech Power
Analyzer Datalogger (model 380803) for both CPU loaded and CPU idle states.
These values are measuring an entire system while the processor is
running under computational load or idle. The Extech Power Analyzer is located
between the main 120AC supply and the PC's power supply.
Given that motherboards vary across these test
systems this is not a "true" measure of CPU power draw alone, but rather a
measurement of the total computer system power draw, which we can compare for
each specific platforms between the CPU idle and CPU stressed states.
| Total System Idle
Power Draw |
| Processor |
Total System Power Draw |
| Intel Pentium 4 540 |
   150 Watts |
| Intel Pentium D 840 |
165 Watts |
| Intel Pentium D 940 |
168 Watts |
| Intel Core 2 Duo E6600 |
117 Watts |
| Intel Core 2 Duo E6750 |
123 Watts |
| Intel Core 2 Duo E8400 |
131 Watts |
| Intel Core i7 920 |
144
Watts |
| AMD Sempron 3600+ |
   120 Watts |
| AMD Athlon64 4000+ |
163 Watts |
| AMD Athlon64 FX-60 |
127 Watts |
| AMD Athlon64 X2 4800+ |
143 Watts |
| AMD Athlon64 X2 5000+ |
156 Watts |
| AMD Athlon64 FX-62 |
168 Watts |
| AMD Phenom II X3 720 |
155 Watts |
 AMD
Phenom II X4 955 |
   148
Watts |
Idle power draw for the Phenom II X4 955 Black Edition PC Systemis actually
quite good (148W), with a power draw that's close to the other quad-core,
Intel's Core i7 920. Since computers tend to spend a lot more time at idle than
they do under full processor load, shaving off even a few watts in idle mode can
shave a lot of money off an electricity bill, given enough time.
| Total System
Stressed Power Draw - All Cores/Threads |
| Processor |
Total System Power Draw (All Cores) |
| Intel Pentium 4 540 |
223 Watts |
| Intel Pentium D 840 (2 Core ) |
240 Watts |
| Intel Pentium D 940 (2 Core Load) |
253 Watts |
| Intel Core 2 Duo E6600 (2 Core Load) |
156 Watts |
| Intel Core 2 Duo E6750 (2 Core Load) |
163 Watts |
| Intel Core 2 Duo E8400 (2 Core Load) |
158 Watts |
| Intel Core i7 920 (8 Thread Load) |
213
Watts |
| AMD Sempron 3600+ |
148 Watts |
| AMD Athlon64 4000+ |
172 Watts |
| AMD Athlon64 FX-60 (2 Core Load) |
196 Watts |
| AMD Athlon64 X2 4800+ (2 Core Load) |
173 Watts |
| AMD Athlon64 X2 5000+ (2 Core Load) |
207 Watts |
| AMD Athlon64 FX-62 (2 Core Load) |
235 Watts |
| AMD Phenom II X3 720 (3 Core Load) |
213
Watts |
| AMD
Phenom II X4 955 (1 Core Load) |
175
Watts |
| AMD
Phenom II X4 955 (2 Core Load) |
197
Watts |
| AMD
Phenom II X4 955 (3 Core Load) |
215
Watts |
| AMD
Phenom II X4 955 (4 Core Load) |
236
Watts |
All four cores of the Phenom II X4 955 BE were then fired
up to full load (236W). To simulate different application configurations,
PCSTATS stressed the cores separately and then together. Under a two core load,
the Phenom II X4 955 BE did well versus other AMD CPus (197W), but couldn't
touch the Intel Core 2 Duos. With all four cores, the 955BE still draws more
power than Intel's Core i7 920 (236W vs 158W respectively), and that's with the
Core i7 chip using HyperThreading to effectively double its multi-threading
capabilities. While AMD has definitely made some gains in terms of power
efficiency, Intel's parts are still the winners here.
Prelude to Benchmarks 
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