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Power Consumption: FX 8150 v i5 2500k v i7 2600k

Last week we reviewed AMD's new FX 8150 processor – the world’s first 8 core desktop chip. Today we are following up with a look at the power consumption when compared against Intel's ever popular Core i5 2500k and Core i7 2600k.

We received many emails and comments asking if we could analyse the power consumption of the three main systems we used in our FX 8150 launch review. Is AMD's FX 8150 an efficient design?

If you missed our review then here are the three systems on test today:

AMD FX 8150 Black Edition
Motherboard: Gigabyte 990FXA-UD7
Cooler: Noctua NH D14
Memory: G-SKill Ripjaws 1600mhz 8GB (2x 4GB)
Graphics Card: HIS HD6970 IceQ Mix
Power Supply: Corsair 850W
Boot Drive: Intel 40GB SSD

Intel Core i7 2600k
Processor: Intel Core i7 2600k
Motherboard: ASRock Fatal1ty Z68 Professional Gen 3
Cooler: Intel XTS-100H
Memory: ADATA 1600mhz DDR3 8GB (2x4GB)
Graphics Card: HIS HD6970 IceQ Mix
Power Supply: Thermaltake Toughpower 850W
Boot Drive: Intel 510 SSD 250GB

Intel Core i5 2500k
Processor: Intel Core i7 2500k
Motherboard: Gigabyte GA-Z68AP-D3 Z68 Motherboard
Cooler: Arctic Cooling Freezer Xtreme Rev.2 CPU Cooler
Memory: Corsair 1600mhz memory 8GB (2x4GB)
Graphics Card: HIS HD6970 IceQ Mix
Power Supply: Corsair 850W
Boot Drive: Patriot Pyro 120GB SSD

We have attempted to keep the systems as closely matched as possible. For instance using the same HIS HD6970 graphics card, and an 8GB DDR3 memory configuration – all running at 1600mhz. There are slight variations between SSD drives and coolers so it is not purely scientific, but the differences would be negligible. All case fans are disabled and the power drain is analysed direct from the socket without a monitor in the mix.

We analysed the power drain when all three systems were at reference clock speeds (Core i5 2500k @ 3.3ghz, Core i7 2600k @ 3.4ghz and FX 8150 @ 3.6ghz). We then increased both Core i5 2500k and Core i7 2600k to 4.6ghz @ 1.45 volts.

The FX 8150 Black Edition voltage was increased by 0.100V+ for complete stability when overclocked to 4.6ghz.

It is worth pointing out again that the Gigabyte 990FXA-UD7 has no bios setting to disable APM (Application Power Management). Without this disabled, the motherboard will maintain the TDP limit when overclocking or overvolting above the limits. As a result APM will throttle some of the cores back to lower Pstates during heavy, multithreaded workloads reducing performance.

To get around this, we have to use AMD OverDrive software (above). We enable TurboCore, apply, then disable TurboCore … this in effect also disables Application Power Management.

Until Gigabyte address this with an updated bios, we have to apply the software ‘fix' to ensure the settings are accurate.

We are testing with Cinebench R11.5 64 bit running on Windows 64 bit Enterprise with all patches applied. All operating systems are identical between system builds. The graphics card is not loaded during this test.

At the default clock speeds, the AMD FX 8150 consumes 94 more watts than the Core i7 2600k. It consumes 112 more watts under load than the Core i5 2500k.

The results above show the power drain from both Core i7 2600k and AMD FX8150 systems when running Cinebench R11.5 64 bit. The results on the left are at reference clock speeds of 3.4 ghz and 3.6ghz respectively. All voltage settings are left at the default values.

The results on the right are when both systems are overclocked to 4.6ghz and loaded with Cinebench R11.5 64 bit – forcing all cores to 100% load. We can see that the FX 8150 system is demanding more power at 3.6ghz than the Core i7 2600k system when overvolted and overclocked to 4.6ghz.

The results are concerning for AMD, especially when factoring in the relative performance levels. The Core i7 2600k is not only a more efficient design, but it uses half the physical cores and still manages to outperform the FX 8150 when at default clock speeds and when both are overclocked to 4.6ghz.

It could be said that the audience who buy these ‘enthusiast' grade processors will not be concerned about a slightly higher electricity bill. After all the flagship GTX 590 and HD6990 still sell very well and these are known to require a lot of power when loaded.

We do feel however that AMD have dropped the ball with the FX8150 in regards to efficiency and power drain. The eight cores can't keep up with the four cores of Intel's Core i7 2600k in the majority of tests we ran and it will certainly be cause for concern for the audience who watch their electricity bill every quarter.

Kitguru says: I do still have a soft spot for AMD's FX 8150, it is an extremely fun chip to play with and overclocking it is a breeze, but this power consumption test has opened my eyes. It seems like a complete contradiction to the energy efficient HD6000 series of graphics card that we have enjoyed for the last year.

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