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AMD's Bulldozer Architecture: Overclocking Efficiency Explored

AMD's Bulldozer Architecture: Overclocking Efficiency Explored
By , Achim Roos

AMD’s FX processor line-up was supposedly designed with efficiency in mind, according to AMD. We're putting this claim to the test, assessing the Bulldozer architecture at a number of different clock rates and comparing the results to Intel's CPUs.

AMD's new FX family was highly anticipated, but its performance simply underwhelmed us. Rather than leap-frogging Intel's mainstream CPUs, it only managed to (at best) match and (at worst) fall behind them. Of course, this is a result of a redesign from the ground-up, which involved certain decisions that affected performance, and others made with power efficiency in mind. In theory, the FX family should be more efficient than its predecessor thanks to AMD's decisions. And a 32 nm manufacturing node would have been thought to help, too.

Just how does the design fare with regard to power as you move frequency around? That's what we're aiming to find out.

There are seven models based on the Bulldozer architecture, presenting a range of clock rates and prices to the folks interesting in dropping one of these chips into a Socket AM3+-based motherboard. For more information about them, check out AMD Bulldozer Review: FX-8150 Gets Tested.

Better Utilization Thanks To Second-Gen Turbo Core

Turbo Core, similar to Intel's Turbo Boost technology, tries to optimize processor performance by evaluating several power-related variables in real time and adjusting clock rate in response. When thermal headroom permits, the feature increase frequency, completing workloads faster and ideally dropping you back to idle more quickly.

From our FX launch story:

"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."

How Efficient is Bulldozer?

Although a superficial examination of AMD's architecture implies some pretty lofty expectations on the efficiency front, enthusiasts only really care about how they translate to the real world. We answered a lot of questions in AMD FX: Energy Efficiency Compared To Eight Other CPUs. However, in that story, we limited ourselves to stock clocks. Here, we're expanding our analysis to overclocking.

We also want to find out where the Bulldozer architecture achieves a balance between low voltage, low power, and decent performance. It's particularly convenient, then, that all of the FX-based processors feature unlocked multiplier ratios. Combined with our test bench's firmware, which lets us easily modify voltage and performance, we're able to fine-tune performance very flexibly. We have six different combinations of clock rate and voltage to explore, so let's get to it.

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Top Comments
  • 32 Hide
    Darkerson , December 26, 2011 4:14 AM
    I know I have been critical in my comments here and there, but I really do hope Bulldozer helps AMD learn and refine Piledriver and future CPUs so that they are all better as a result. I know I will be skipping BD, but that doesnt mean I dont ever want to use AMD again. I will always root for the underdog, in hopes that we have another Athlon 64 on our hands again.
  • 30 Hide
    aznshinobi , December 26, 2011 3:47 AM
    Reading conclusion paragraph, I'd have to agree. I think they probably would've been better of using the STARS arch and just die shrinking it to 32nm.
  • 20 Hide
    Anonymous , December 26, 2011 8:20 AM
    Tom's Hardware finds that overclocking increases speed, power requirements. Film at 11.
Other Comments
  • 30 Hide
    aznshinobi , December 26, 2011 3:47 AM
    Reading conclusion paragraph, I'd have to agree. I think they probably would've been better of using the STARS arch and just die shrinking it to 32nm.
  • 32 Hide
    Darkerson , December 26, 2011 4:14 AM
    I know I have been critical in my comments here and there, but I really do hope Bulldozer helps AMD learn and refine Piledriver and future CPUs so that they are all better as a result. I know I will be skipping BD, but that doesnt mean I dont ever want to use AMD again. I will always root for the underdog, in hopes that we have another Athlon 64 on our hands again.
  • 5 Hide
    deadon2 , December 26, 2011 4:49 AM
    Fehh... did my build on a 990fx platform with a 955be CPU. Runs plenty fast, and I can upgrade the AM3+ in a year when AMD gets it right.

    Although I appreciate the work done on this article...

    Nothing to see here folks, move along...
  • 17 Hide
    dontcrosthestreams , December 26, 2011 5:34 AM
    im just fine with my 110$ 955be.... 29 deg idle at 3.7ghz
  • 4 Hide
    noob2222 , December 26, 2011 6:03 AM
    Is that a typo on page 7 and 8? "Clock Frequency: 4.5 GHz, Multiplier: 22.5x, CPU Voltage: 1.428 V" cpu-z shows 1.380? page 8 cpu z shows 1.44 and not 1.5.

    As for my own efficiency testing, I achieved 1.375V (cpu z), 4.4Ghz out of my 8120 with ease. I upped the NB to 1.115v (+.015V)wich added more stability and clocked the NB to 2600 to match HTT, wich brought another 1gb/s on sandra's memory test. All without disabling C1E or C3 states.

    Would be nice to see some followups with memory testing, BD responds to fast speeds. Hard to read since its in a different language but the graphs are easy enough to see
    http://www.planet3dnow.de/vbulletin/showthread.php?t=401023&garpg=13
  • 20 Hide
    Anonymous , December 26, 2011 8:20 AM
    Tom's Hardware finds that overclocking increases speed, power requirements. Film at 11.
  • -1 Hide
    de5_Roy , December 26, 2011 8:29 AM
    yay! another efficiency article from toms. :love: 
    sad to see amd's claims about efficiency turn out to be (much) less than accurate.
    some people are definitely gonna complain about the ram used (ddr3 1333) and windows 8 or lack of highly threaded benchmarks like truecrypt encryption or pov ray tracing (as if those are always used by regular users lol) and stuff.
    undervolting does look promising...but it doesn't seem to make any difference compared to sandy bridge systems. worse, bulldozer needs voltage increase to get more clockspeed.. i guess it will be more evident in fx 4100 and 6100 where substantial core voltage increase is necessary to get stock sandy bridge level performance out of them. that's just disappointing.
  • 3 Hide
    memadmax , December 26, 2011 9:51 AM
    It seems to me that Bulldozer is either a AMD bastard child chip, or it's a first gen chip of which subsequent generations of the architecture will be playing "catch up" performance wise. Otherwise, it's typical AMD trying to be efficient rather than a heavy hitter.

    But if you ask me, this is a "defensive" chip in the processor wars. And no war has been won playing defense.
  • -2 Hide
    de5_Roy , December 26, 2011 10:05 AM
    in any war, the best defense is a good offense. and amd has managed to offend most of the people who liked their cpus (fanboys excluded, obviously).
  • 9 Hide
    murambi , December 26, 2011 10:08 AM
    This article feels like when you are kicking a dog when its down. I really wanted AMD to challenge intel in the performance crown segment
  • 5 Hide
    salgado18 , December 26, 2011 10:22 AM
    pafnucyTom's Hardware finds that overclocking increases speed, power requirements. Film at 11.

    Conclusion is stupid, but the tests are relevant. Nice article.
  • 6 Hide
    technoholic , December 26, 2011 10:38 AM
    My latest decision about BD is that it is not a matured product YET. No, the war isnt lost, only 1 or 2 fronts are lost and that doesnt mean the war is lost. The ultimate problem of this chip is that it needs much power to operate. I am not a tech geek or a pro in CPU architecture but i think that AMD needs to do some improvements in the architecture, too (also in software side)

    Maybe some people will criticize me for this but i always like the most updated/newest approaches in tech; not the older and faster. But newer approaches mostly suffer from immature designs. However, i believe we will see some excellent CPUs from AMD in the near future. Because at least the idea behind this architecture is not worse than that of phenoms. Let's not forget, giant firms like Intel also had many failures in their history (remember pentium 3 was a mediocre design and 4 was much worse), but they managed to advance further with their new ideas. I am sure in this moment AMD guys are working hard on their next big step.
  • -2 Hide
    g4114rd0 , December 26, 2011 10:54 AM
    Start and end each attack and defence pattern with a poise pattern,
    such as Single Scorpius emerges from Cave,
    which can also be use for attack or defence.
  • -7 Hide
    theuniquegamer , December 26, 2011 10:58 AM
    Its true that amd's stock coolers are not efficient as the intel's . Because i have both intel i5 760k and amd 955be system , the amd system runs so loud at 40c on stock settings (idle) and the intel runs at above 57c on stock (idle). It makes noise after 70c.(I am not comparing intel with amd because intel i5 is 32nm amd 955 is 45nm). So i think amd should provide good quality stock coolers in the black edition cpus. I
  • 6 Hide
    zooted , December 26, 2011 11:03 AM
    ^Amd's stock coolers are better.
  • -6 Hide
    Anonymous , December 26, 2011 11:31 AM
    Did AMD specifically ask Tom's and Anand to show their CPUs on the front page covered with thermal paste and generally looking dirty and unattractive, or did Intel specifically request it? I have a hard time believing that both of you came up with the same stupid idea.

    In other news, your desktop PC has relatively low power requirements compared to every other appliance in you house, if you think you need to worry about a lousy few watts, you'd probably be better off switching to more efficient light bulbs and finding a lower wattage coffee pot first.
  • -6 Hide
    elbert , December 26, 2011 11:59 AM
    I stopped reading when I seen 1333 memory. If you don't show Overclocked memory past 1866 I don't want to waste my time.
  • 1 Hide
    Yuka , December 26, 2011 12:12 PM
    200.7Mhz HT Link?

    I almost stopped reading there, but I remembered it was an efficiency run.

    It's nice too see they suffer from the same problem the Phenoms do. AMD over estimates voltage with their CPUs, so at default-everything it's going to be more power hungry. With a nice tunning, they can run as cool as their Intel counterparts (cool, but not as fast, sadly).

    Good to see they also over estimated stock voltages for the FX line; gives me hope for low power CPUs.

    Cheers!
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