The launch of Bulldozer in October wasn't exactly a success for AMD. In our review, Anand ended up recommending the Intel i5-2500K over AMD FX-8150. One of the reasons behind the poor performance of Bulldozer is its unique design: each Bulldozer module consists of two integer and one floating point core. Todays operating systems don't know how to optimally schedule threads for this design and as a result, the full potential of Bulldozer has not been achieved. Microsoft has released a hotfix for Windows 7 and Server 2008 R2 that should increase the performance of Bulldozer.

Let's look at the problem to see what happened and how the hotfix helps address it. Before the update, Windows didn't know how to ideally schedule threads on Bulldozer. Essentially, it didn't know when it was good to place threads on single module versus multiple modules.

The picture above explains this pretty well. Before the update, Windows more or less randomly placed the threads which meant many modules were unnecessarily active at the same time. This capped the maximum Turbo speeds because those can only be achieved when some of the modules are inactive (power gated).

VR-Zone is claiming that Windows sees one Bulldozer module as a single multi-threaded core, similar to an Intel Hyper-Threading core. Basically, your 8-core FX-8150 is seen as a quad-core, 8-thread CPU—just like Intel's i7-2600K for instance. This goes against AMD's design and marketing because Bulldozer is closer to an 8-core CPU.

We have not yet tested Bulldozer with the hotfix, but don't expect miracles as Microsoft is suggesting a 2-7% increase. Better scheduling for the Bulldozer CPUs will improve performance a bit, but not enough to close the gap in many scenarios. Windows 8 already has the new thread scheduler, and according to AMD's own and third party tests the performance increase is up to around 10%, but Bulldozer needs a lot more than 10% to surpass Sandy Bridge.

Update: VR-Zone reports (and we can confirm) that the download link for the hotfix is no longer functional. There were apparently unexpected performance drops in some cases after applying the hotfix and Microsoft is investigating the issues. Modifying the scheduler in Windows is not something to be done lightly, as it changes a core element of the OS, so more testing and validation for such updates is always a good idea.

Update 2: Apparently there is a second part to the hotfix that was not pushed live, and this hotfix was pushed live prematurely.

Source: Microsoft

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  • kennii - Sunday, December 18, 2011 - link

    I need this cause for XMAS
  • ShieTar - Monday, December 19, 2011 - link

    I don't assume this patch will really change much in any scenario where CPU power is critical, as such cases should not be a 3-thread case as described in the graphic in this article.
    3-Thread applications tend to be games, but they will be GPU limited in about 99% of all cases, because that is how people buy: Almost nobody will run a 40$ CPU along a 500$ GPU.
    Or your software is either singlethreaded, so that scheduling should play no role, or highly multithreaded, where 8 Threads are used and the scheduler is out of options anyways.

    I could be wrong, but personally I expect to see the only differences in gaming benchmarks done in ultra-low resolutions.
  • Dragan - Tuesday, December 20, 2011 - link

    I gave up on my Q6600 it has a good CPU and I don't see any reason to upgrade!
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  • Belard - Tuesday, December 20, 2011 - link

    I'm building a system for one of my clients with parts from a local store. I priced out the system with 3 different kinds of CPUs. The MicroCenter store is offering $50~30 off for CPU and Mobo combos for Intel and AMD... Other than the CPU and mobo, the entire system with Win7Home has the same parts.

    $650 = Intel i5 2500k (Gigabyte board with USB 3.0)
    $600 = AMD X4 970 (Gigabyte 880 board)
    $720 - AMD FX 8150

    I told my client, spend the $50 extra and get a system that is up to 50% faster roughly... depending on the application. The FX 8150... not much better.
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