AMD Bulldozer Review: FX-8150 Gets Tested

Power Management

Each Bulldozer module is on its own clock domain, meaning multiple modules can operate at different frequencies simultaneously. This is new functionality compared to Phenom II, which ran its cores at the same speed (but had a number of intermediate p-states from which to choose). However, AMD tried this approach on its original Phenom.

If you remember back far enough, separate clock domains caused a problem with Phenom processors in Windows Vista when Cool’n’Quiet was enabled. Through a process called migration, the operating system’s scheduler would move threads between cores in an effort to maintain symmetry under load. Why? From my Intel Lynnfield launch story:

“In order to maintain the symmetry of a system under full load, you don’t want I/O to become dependent on just one core. If you keep threads rotating between cores running at their maximum performance (this whole concept goes out the window when you start talking about spinning cores down), you get better responsiveness.

This was an implementation decision made during Microsoft’s Windows NT kernel design, and based on our experiences with both processor vendors' hardware, it wasn't considered a "feature" to either company. Of course, it affected Intel in a much different way than AMD. The problem Intel had in Vista was one of power consumption. For every migration, you had to write-combine the Nehalem architecture’s L3 cache, which cost power.

This changes with Windows 7 and a feature called ideal core. If a task’s needs are being addressed by one core, the operating system will let you stay there. This means two things to Intel: first, you don’t use power on the migration, and second, idle cores are able to remain in a C6 state. Purportedly, this migration fix alone will yield an extra 10 to 15 minutes of battery life on Nehalem-based notebooks, though this won’t become a major issue until the mobile dual-core Arrandale launches later this year. Perhaps more interesting, though, is that processors without C6 will not realize this gain (including AMD’s CPUs).”

So, while Phenom may have been a bit before its time given Vista’s scheduler, Windows 7 should handle AMD’s design in a more elegant manner. But even beyond that, Larry Hewitt, chief SoC engineer for Zambezi, Interlagos, and Valencia, says that the time it takes Bulldozer to spin up from its minimum p-state is less than it was on Phenom.

Naturally we wanted to put Larry’s claim to the test. You can’t see this in the graph up above, but the Phenom II, which fixed Phenom’s migration problem by running cores at the same speed, sees no performance difference in PCMark 7 with Cool’n’Quiet on or off, just as we'd expect. The same goes for FX-8150, confirming that Zambezi and Windows 7 behave themselves. What’s really interesting, though, is how effective AMD’s power-oriented optimizations to Bulldozer really are. The blue and green lines are the FX and Phenom II X6 with CnQ turned on. Black and red are the same two chips with CnQ turned off (again, respectively).

We find that the Phenom II X6 averages 204 W of system power use with CnQ turned off and 191 with it turned on—a 13 W difference. The FX-8150 averages the same 191 W with CnQ enabled, but it jumps up to 240 W with the feature turned off. On average, CnQ cuts system power use by an astounding 49 W during the benchmark run, without negatively affecting performance!

The integrated northbridge and L3 cache complex is on its own clock domain. Additionally, it has its own power domain. Power gating, which was introduced by Intel in its Nehalem design but only just implemented by AMD in the Llano-based APUs, is purportedly used extensively in this SoC to minimize leakage current when parts of the chip aren’t in use.

As with Llano, Zambezi/Valencia/Interlagos-based chips support the Core C6 state, where a Bulldozer module’s cache is flushed, its context is exported to system memory, and all voltage is removed from it. The result is that, for every module you can put to sleep, power consumption and heat dissipation both drop. This is doubly beneficial taken in context with the Windows 7 migration issue I just mentioned, which should allow idle Bulldozer modules to stay off longer (this has to happen at the module—not core—level).

C1E support isn’t anything new for AMD, but it’s improved in that all of the Bulldozer modules can be power gated, as the northbridge, HyperTransport links, and DRAM are all dropped into a very low power state.

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    Top Comments
  • Homeboy2
    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.
    55
  • jdwii
    Been so long and i'm kinda sad.
    52
  • gmcizzle
    What I learned: the 2.5 year old i7-920 is still a beast.
    48
  • Other Comments
  • btto
    yeah finaly, now i'll read it
    -25
  • ghnader hsmithot
    nOT Bad AMd!
    -35
  • jdwii
    Been so long and i'm kinda sad.
    52
  • compton
    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.
    43
  • ghnader hsmithot
    At least its almost as good as Nehalem.
    29
  • gamerk316
    Dissapointing. Predicted it ages ago though. PII X6 is a better value.
    40
  • Anonymous
    As I expected - failure.
    26
  • AbdullahG
    I see the guys from the BD Rumors are here. As many others are, I'm disappointed.
    25
  • iam2thecrowe
    for the gaming community this is a FLOP.
    33
  • phump
    FX-4100 looks like a good alternative to the 955BE. Same price, higher clock, and lower power profile.
    25
  • phatbuddha79
    Why bring back the FX brand for something like this?
    40
  • gmcizzle
    What I learned: the 2.5 year old i7-920 is still a beast.
    48
  • jdwii
    This is sad, I'm still getting it as its my only option i'm getting a 8120 Toms why did you only review a 8150 when they have all of them on other sites?
    -25
  • ern88
    What I've learned is...AMD=FAIL!!!!!
    -31
  • killerclick
    As I said before, it won't come close to beating Intel in performance or price. Now let's hear the fanboys whine.

    Buh-bye AMD, buh-bye!
    -35
  • Ragnar-Kon
    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
  • Tamz_msc
    So Bulldozer is AMD's version of NetBurst?
    24
  • Homeboy2
    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.
    55
  • killerclick
    homeboy2Everyone 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.


    Intel shouldn't lower prices, they should raise them. I'll gladly pay more to reward competent product development and nothing would please me more than AMD going down in flames for all their flops in the past 5 years. Intel doesn't need AMD to push them forward.
    -35
  • the associate
    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...
    11