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Enabling Turbo Core

AMD Bulldozer Review: FX-8150 Gets Tested
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Back when AMD launched its Phenom II X6 1090T, it debuted a feature called Turbo Core. It was supposed to be an answer to Intel’s Turbo Boost capability, which would capitalize on available TDP in poorly-threaded workloads (where other cores simply sat idle) to increase clock rate.

As you know, Turbo Boost (Intel’s feature) employs an on-die power controller that evaluates temperature, current, power consumption, and operating system states. With all of that information, it can shut down idle cores, freeing up thermal headroom to accelerate active cores. The degree of acceleration is contingent on how many cores are in use. Obviously, there’s a lot more room to ratchet up clock rate in a single-threaded application. As a result, you end up with a frequency map of sorts that scales up and down depending on the parallelism of any given application. As a quick example, from Intel Core i5 And Core i7: Intel’s Mainstream Magnum Opus:

Turbo Boost: Available Bins (Under TDP/A/Temp)
Processor Number
Frequency
4 Cores Active
3 Cores Active
2 Cores Active
1 Core Active
Core i7-870
2.93 GHz
2
2
4
5
Core i7-860
2.8 GHz
1
1
4
5
Core i5-750
2.66 GHz
1
1
4
4
Core i7-975
3.33 GHz
1
1
1
2
Core i7-950
3.06 GHz
1
1
1
2
Core i7-920
2.66 GHz
1
1
1
2


Turbo Core (AMD’s feature), in comparison, was presented as a deterministic feature that turns on in lightly-threaded workloads where three or fewer cores are active, or off altogether when an application taxes anything more than three cores. In practice, it didn’t seem nearly as binary as AMD described. What I saw in AMD Phenom II X6 1090T And 890FX Platform Review: Hello, Leo was that cores would jump to many different frequencies, never really settling on what was suggested as the top Turbo Core clock rate. As a result, performance gains attributable to Turbo Core seemed more modest than what I expected.

Fortunately, AMD says it made some changes to the technology for Bulldozer that should improve its effectiveness compared to Thuban.

FX Does Turbo Core A Little Differently

Application Power Management (APM) describes Zambezi/Valencia/Interlagos’ ability to monitor (in real-time) the amount of power each core consumes. Rather than taking thermal or current measurements, the activity of each Bulldozer module is tracked. AMD knows how much power each operation requires and is able to come up with instantaneous power use on a per-module basis. A quick comparison between real consumption and maximum TDP indicates whether or not there’s headroom to increase performance. In an example where you’re running an application that doesn’t tax the processor’s resources, Turbo Core dithers between the processor’s base frequency and a higher clock rate, jumping between them to average better overall performance at the defined TDP.

Turbo Core isn’t limited to just a base and some arbitrarily higher frequency, either. It’s actually implemented in three p-states: the base (referred to as P2), an intermediate state (P1), and a higher state (P0). That’s an improvement over the first-gen version of Turbo Core, which AMD says only switched between two p-states. And it’s significant, too, because you can enter P1 with all eight cores active, so long as the headroom is there. Stepping up to P0 requires at least two of four modules to idle. AMD does allow the chip’s TDP to be exceeded instantaneously, but of course it can’t hold that for any thermally significant amount of time.

As such, when you look at the specs for an FX processor and see CPU Base, CPU Turbo Core, And CPU Max. Turbo, you are guaranteed to always get at least that base frequency. You’ll see the Turbo Core clock rate so long as TDP is in check (as it would be in a well-threaded workload that doesn’t exceed the processor’s thermal ceiling). And, whenever half of the chip’s cores are idle, it’s possible to realize maximum Turbo Core speeds.

In the top chart, we see Turbo Core’s effect on iTunes, a single-threaded title. Because seven of its eight cores are essentially idle in this metric, the FX-8150 is allowed to dither at up to 4.2 GHz (it doesn’t hold that frequency constant; rather, it bounces between P1 and P0, or 3.9 and 4.2 GHz). The result is a 10-second shave compared to the same test running without Turbo Core turned on, yielding a flat 3.6 GHz.

The chart below is indicative of 7-Zip, a more thoroughly threaded application able to tax all of the -8150’s resources. Again, you don’t get a constant 3.9 GHz. With Turbo Core enabled, FX-8150 dithers between 3.9 and 3.6 GHz (versus a straight 3.6 GHz with the feature disabled). The resulting two-second speed-up is pretty modest. Even still, we have to appreciate the “free” performance that wouldn’t have been possible in first-gen Turbo Core limited to two p-states.

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Top Comments
  • 54 Hide
    Homeboy2 , October 12, 2011 4:38 AM
    killerclickAs I said before, it won't come close to beating Intel in performance or price. Now let's hear the fanboys whine.


    Everyone should cry, even the Intel fanboys, this is bad news for everyone, now Intel has absolutely no incentive to lower prices or accelerate Ivy Bridge.
  • 51 Hide
    jdwii , October 12, 2011 4:14 AM
    Been so long and i'm kinda sad.
  • 47 Hide
    gmcizzle , October 12, 2011 4:25 AM
    What I learned: the 2.5 year old i7-920 is still a beast.
Other Comments
  • 51 Hide
    jdwii , October 12, 2011 4:14 AM
    Been so long and i'm kinda sad.
  • 43 Hide
    compton , October 12, 2011 4:16 AM
    Not many surprises but I've been waiting for a long, long time for this. I hope this is just the first step to a more competitive AMD.
  • 29 Hide
    ghnader hsmithot , October 12, 2011 4:16 AM
    At least its almost as good as Nehalem.
  • 40 Hide
    gamerk316 , October 12, 2011 4:17 AM
    Dissapointing. Predicted it ages ago though. PII X6 is a better value.
  • 26 Hide
    Anonymous , October 12, 2011 4:18 AM
    As I expected - failure.
  • 25 Hide
    AbdullahG , October 12, 2011 4:18 AM
    I see the guys from the BD Rumors are here. As many others are, I'm disappointed.
  • 33 Hide
    iam2thecrowe , October 12, 2011 4:20 AM
    for the gaming community this is a FLOP.
  • 25 Hide
    phump , October 12, 2011 4:22 AM
    FX-4100 looks like a good alternative to the 955BE. Same price, higher clock, and lower power profile.
  • 40 Hide
    phatbuddha79 , October 12, 2011 4:25 AM
    Why bring back the FX brand for something like this?
  • 47 Hide
    gmcizzle , October 12, 2011 4:25 AM
    What I learned: the 2.5 year old i7-920 is still a beast.
  • 25 Hide
    Ragnar-Kon , October 12, 2011 4:36 AM
    Looks like solid chips, but I'll admit that the price point isn't low enough to compete in the gaming world with Intel.

    I am rather curious how the FX-4100 will stack up against the current Phenom II X4 chips.

    And even though the FX is a slight disappointment, I am rather impressed by the Windows 8 benchmarks. Having said that, by the time Windows 8 is ready for release I'm sure Intel will have an even better solution.
  • 25 Hide
    Tamz_msc , October 12, 2011 4:37 AM
    So Bulldozer is AMD's version of NetBurst?
  • 54 Hide
    Homeboy2 , October 12, 2011 4:38 AM
    killerclickAs I said before, it won't come close to beating Intel in performance or price. Now let's hear the fanboys whine.


    Everyone should cry, even the Intel fanboys, this is bad news for everyone, now Intel has absolutely no incentive to lower prices or accelerate Ivy Bridge.
  • 12 Hide
    the associate , October 12, 2011 4:41 AM
    killerclickAs I said before, it won't come close to beating Intel in performance or price. Now let's hear the fanboys whine.


    Waaaahhhhhhhhhhhhh!!!!!!!!

    Bah, well, been with AMD since my first pc like 8 years ago...Guess I'll be going intel for the first time ever especially since I can get an overkill cpu for just 300 bucks. Hell that's how much I payed for my phenom II 955...
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