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Six-Core Analysis: AMD’s Phenom II X6 Gets Scaled Down

Six-Core Analysis: AMD’s Phenom II X6 Gets Scaled Down
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What’s the real benefit of six cores versus five, four, three, two, or one? This article looks at the performance, power, and efficiency of AMD's Thuban-based six-core Phenom II X6 1090T processor running with several different core configurations.

Depending on core counts, cache, and power consumption, processors may not be running at their "best" with all cores enabled. After all, AMD's Thuban-based Phenom II X6 1055T and 1090T share the same 6MB L3 cache as the manufacturer's Phenom II X4s, X3s, and X2s.

Today we're looking into the new Phenom II X6 processor's performance, power consumption, and efficiency by testing it with all possible core counts, from six down to one.


Most people wouldn’t think of disabling processor cores. After all, you’d assume that people buy six-core CPUs for a reason. However, our numbers show how well the Thuban architecture can scale performance and power as its core count climbs. In the end, six cores are certainly fastest under threaded workloads, but they don't necessarily deliver the best power efficiency. Also, the leap from four to six cores might not be as significant to you as the move from two to four cores.

Looking at the differences between four and six cores makes sense from another perspective: as you could see in our article Meet Zosma: AMD’s Quad-Core Phenom II X4 960T Gets Unlocked, it's possible to unlock some AMDs processors to get additional processing cores. Whether or not this unlocking is reliable is a different story, though, as the six-core processor was probably turned into a quad model because of yield issues on one or two cores. This is why you should run extensive reliability testing before even thinking about putting the system into commission.

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  • 1 Hide
    mi1ez , 24 June 2010 16:16
    An ok article, but I would have been interested to see maximum overclock at each point, even if it was without a full set of benchmarks.
  • 2 Hide
    silverblue , 24 June 2010 19:42
    Now if only AMD can upgrade its L3 cache technology...
  • 2 Hide
    aje21 , 24 June 2010 20:09
    Why is the system idle power so much higher than the system peak power (until you get to 6 cores when it's a match)?
  • 2 Hide
    aje21 , 24 June 2010 20:11
    aje21Why is the system idle power so much higher than the system peak power (until you get to 6 cores when it's a match)?

    Ah, because they should be %age graphs but the legend is in Watts. Doh!
  • 1 Hide
    Anonymous , 25 June 2010 16:39
    Is the diminishing performance improvement as cores are added perhaps due to the L3 cache memory bottleneck? This diminishing return on extra cores has been highlighted in many previous articles, I was just wondering how much of the story is explained by the memory bottleneck as opposed to other I/O resource bottlenecks.
  • 1 Hide
    Anonymous , 25 June 2010 20:35
    Good to see that our article on Multi-Core efficiency on the 1090T here:

    http://www.hardwarereview.net/Reviews/AMD%20Phenom2%20X6-1090T/AMD-Phenom2-X6-1090T.htm

    has spurred others onto focusing on this crucial area given that raw clock speeds have hit a ceiling some time ago.

    Keep up the good work (AT has the resources to run far more tests more thoroughly than we could)
  • 0 Hide
    Anonymous , 26 June 2010 01:19
    It really shows that unless you are doing media encoding/transcoding, you will have little use for more than 2 cores.
    But even with that application, adding cores beyond 3 or 4 starts to equal diminished returns. Clearly it is because it is hitting the memory bandwidth wall. Guess we need DDR5 RAM. :) 
  • 0 Hide
    silverblue , 26 June 2010 16:40
    A triple/quad channel controller plus larger L3 cache should help a bit. :) 
  • 0 Hide
    ksampanna , 26 June 2010 21:40
    Nothing that we all here didn't already know about.
  • 0 Hide
    Silmarunya , 27 June 2010 22:11
    MPUKIs the diminishing performance improvement as cores are added perhaps due to the L3 cache memory bottleneck? This diminishing return on extra cores has been highlighted in many previous articles, I was just wondering how much of the story is explained by the memory bottleneck as opposed to other I/O resource bottlenecks.


    In the Phenom II it clearly is a bottleneck (although a relatively minor one). But the Intel i7-980X saw its L3 cache increased by a third, just like its core count, and there still was a diminishing return. A smaller one, but still.

    However, as for the Phenom II it's impossible. They could never have stayed within the 95W/125W power limit with additional cache (unless AMD would have opted for a die shrink, massively increasing development time). And that would have posed a problem as not all AM3 boards support 140W and none can go higher. A bad signal for a company that has backwards compatibility as one of its prime selling points...