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AMD FX-8350 review: is AMD back?
by Marc Prieur
Published on November 28, 2012

Energy consumption and efficiency
For the energy consumption test we tried to use a test which is more or less representative for all architectures of what we get in applications in terms of performance and energy consumption. In the end we opted for Fritz Chess Benchmark once again. In addition this application has the advantage of allowing us to fix the number of threads to be used.

The energy consumption readings therefore shouldn't be taken as absolute maximum values but rather as typical of a heavy load - applications specialised in processor stress such as Prime95 can consume up to 20% more. All energy economy features, including those on motherboards such as the ASUS EPU, were turned on for this test, as long as they didn't have a negative impact on performance.

Remember we give two types of readings, the first at the 220V wall socket using a wattmeter for the whole test configuration and the second at the ATX12V via a clip-on ammeter. This reading allows us to isolate the energy consumption of the processor for the most part, but unfortunately it isn’t exactly comparable from one platform to another because in certain cases a small proportion of the energy consumption of the CPU comes from the standard 24-pin ATX socket.


[ 220V socket ]  [ ATX12V ]

The AM3+ platform draws quite a lot of power at idle in comparison to the LGA1155 platform, an issue that AMD has resolved on FM2. In this domain the FX-8350 does a bit better than the FX-8150 and is the most economical AM3+ CPU. In load the energy consumption of the FX-8350 is notably lower than the FX-8150 with one thread but moves back slightly above it with eight threads. All in all, these readings are reassuring given the higher voltage required by the FX-8350, proof of better handling of current leakage.

There’s a huge gap to the Intel processors and the low energy consumption on the last Core i3-3240 is particularly impressive: less than 23w in load on the ATX12V!

We now move on to our representation of energy efficiency. To get this you have to divide the performance levels obtained in Fritz Chess Benchmark by CPU energy consumption. The only problem is however that it’s impossible to get an exact reading of CPU consumption: the readings at the ATX12V aren’t 100% comparable from one platform to another and the reading at the socket doesn’t allow us to isolate CPU consumption entirely.

We therefore decided to use two methods to look at processor consumption:

- Energy consumption at the ATX12V
- 90% of the difference in energy consumption between load and idle at the socket

We took this at 90% so as to exclude power supply yield. Note that while the first reading favours processors that draw a small proportion of power from the standard ATX socket, the second favours those with high energy consumption at idle. Unfortunately no method is perfect.



[ 220V socket ]  [ ATX12V ]

Even if Fritz is the application that benefits least from the Piledriver architecture as we'll see a little further on, the higher clock combined with energy consumption that remains close to the FX-8150 allows the FX-8350 to be more efficient whether with one or eight threads. With multithreading it is however less efficient than the Phenom II X6s.

The Intel offer is completely out of reach. A Core i5 or i7 Sandy Bridge is around 2x more efficient than the AMD FX-8350 and the Ivy Bridges go even further!

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