To assure consistency, we disabled hard drive power down and simply allowed the drive to return to idle, watching the meter until power consumption normalized. We then used the power analyzer's "MAX" holding feature to collect readings for ten minutes.

Rated at only 35 W TDP, peak power consumption for the entire Athlon 64 X2 3800+ Energy Efficient Small Form Factor platform reached a mere 80 W under full CPU load, quickly dropping to 54 W at idle. The Athlon 64 X2 4600+ Energy Efficient configuration was no power monger either, using 101 W under full load and 56 W while idle.

As expected, the "89 W" Athlon 64 X2 3800+ standard version was able to draw less power than the "65W" Athlon 64 X2 4600+ Energy Efficient processor, proving that the standard parts are able to operate well below their maximum ratings even at maximum CPU load.

The Core 2 Duo platform drew significantly more power than the similarly-performing Athlon 64 X2 4600+ Energy Efficient system at both idle and maximum CPU load. The 14 W difference at full load seems trivial to performance enthusiasts, but more significant was the 45% greater consumption when idle. AMD's superior efficiency is quite obvious in this sample set.

Conclusion

With its total system power consumption of 54 W idle and 79 W at maximum load, the Athlon 64 X2 3800+ Energy Efficient Small Form Factor CPU lives up to its efficiency claims. The same platform, however, also drew less than 100 W at maximum load using the standard Athlon 64 X2 3800+. When discussing total system power consumption, it's important to remember that it includes chipset, graphics, RAM and hard drive power, and even the 15-25% power typically wasted by the power supply during conversion.

Two things became overwhelmingly obvious during this test: AMD's power savings extend from enhanced versions to standard Athlon 64 X2 cores, and that platform efficiency (mostly chipset and graphics) is the key to keeping overall power consumption at manageable levels. High efficiency will allow smaller enclosures for portable PCs and low noise cooling in home theaters, without resorting to typically high-priced mobile components or low-performance down market processors.

Intel's release of Core 2 may have stolen AMD's performance-per-clock thunder, but AMD retains its advantage in performance-per-watt when including the platform.

Author's Opinion

Were Athlon 64 X2 Energy Efficient processors to reduce average power use by 10 W, the average 10 hour per day office system would cost only few dollars less per year to operate. Multiplying that cost savings over 100 systems, an office manager might save enough to pay for the beverages at the annual Christmas party. If the system could last 10 years, the savings might pay for the cost difference between the standard and enhanced version.

The best reason this author can find to justify the added expense of low-wattage Athlon 64 versions is for silent cooling in HTPC enclosures, which often reach their peak heat output during movie viewing. After all, the last thing you'd want in a home theater is a noisy fan kicking in during a quiet movie scene. Peak output being more important than averages when it comes to cooling, the "Energy Efficient Small Form Factor" name seems appropriate - if a bit long.

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