Power Consumption

When we test power consumption we consider it as a whole platform, so whether the CPU includes a memory controller or it's separate in the northbridge, this doesn't make a difference to what we measure at the wall and how much electricity is paid for. The setup other than the motherboard and CPU is kept consistent to provide uniformity where possible.

Despite power saving hardware on the Intel motherboard, it was not used in order to keep the power saving results limited to the CPU only.



The AMD 65nm K10 CPUs were never really that power efficient, and despite the Cool'n'Quiet dropping the CPU clock to half of full speed (whereas the K10.5 chips drop it further to a fixed 4x multiplier), they still use 25 percent more juice under idle than the previous K8s and Intel's E5200. Under load though and the Intel 45nm CPU saves nearly 40 percent more power at stock speeds and voltages - a clear saving compared to the Kumas. Between the 7850 BE and 7750 BE, there is very little variation - strangely the 7750 used slightly more power under idle, but that could be down to a manufacturing difference because it actually drops to a frequency that's 50MHz lower than the 7850 BE's idle speed.

Value and Conclusions

The performance of the 7850 Black Edition is unsurprisingly underwhelming compared to the 7750 Black Edition we looked at just four months ago. For a 100MHz speed bump, it offers no additional overclocking headroom because it's still the same 65nm B3 core, and so the limitations are still there.

In just a few tests, multitasking in particular, the K10 core with its improved memory access, better bandwidth, L3 cache and overall lower latency does benefit over the Intel E5200, even with overclocked. However, for the most part, the Intel is far, far more overclockable - we hit 4GHz, stable with relative ease - and it affords a massive chunk more performance.


At £62, the 7850 Black Edition launches cheaper than the 7750 BE back last year, but the 7750 BE is now £49 - over 26 percent cheaper. For home theatres and multi-taskers on a budget, the 7750 Black Edition combined with 4GB of cheap 1,066MHz memory and an Nvidia GeForce 8200 or AMD 780G motherboard affords a very capable PC for a nose over £150.

Unfortunately for the 7850 Black Edition, you get virtually the same core performance and identical overclocking headroom from the Athlon X2 7750 Black Edition - you're best off keeping the £13 difference in your pocket because the price premium just isn't worth it. Ultimately, AMD needs to move its dual cores to 45nm as soon as possible, preferably with no transistor and temperature intensive L3 cache, and then we'll really see them fly. Until that happens though, we expect overclockers to still buy the £60 Intel Pentium Dual Core E5200.

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Score Guide