AMD Bulldozer FX-8150 Processor Review

Author: MAC
Date: October 11, 2011
Product Name: AMD FX-8150
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Feature Test: Turbo CORE Technology

As you all know by now, the Turbo CORE technology that AMD first introduced on the Phenom II X6 processors has found its way onto Zambezi, and with great effect! So you want to know how AMD's implementation of Turbo CORE works? Well let us direct you to the following chart:

Confused? Don't worry, we were too. Here is a very basic explanation.

Processor performance states (P-States) are effectively supported operating frequencies and voltages that the processor can switch between in order to manage power consumption and lower heat output. These states are controlled by the ACPI function in the operating system. Processors can move in and out of these P-states in a manner that is seamless to the user. The lower the P-state number the higher the processor speed.

As we mentioned previously, AMD is very conservative with their TDP estimates, and as such their processors usually have a considerable amount of TDP headrom. With that in mind, AMD have devised a two-tier Turbo implementation for Zambezi. There is Turbo Core and there Max Turbo. Turbo Core can increase the frequency the frequency of all eight cores by up to 300Mhz when there is extra TDP headroom. It's not infinite turbo though, since power consumption increases as the amount of threads being used increases. Therefore, once the TDP limit has been attained, the AMD Power Manager will ramp down to a P-state that is within the TDP. Eventually, when additional headroom is once again available, then it will Turbo up to higher performing P-state.

Max Turbo is a new mode that is engaged on lightly-threaded workloads. It can increase the frequency of half the cores by up to 600MHz, and keep that higher P-state for a much longer time than previous turbo iterations.

Here is how the Turbo Core implementation looks like in real-time:

In our experience, with the FX-8150 you can expect between 3900-4200Mhz when using 1 to 4 cores, and 3600-3900Mhz when using between 5 to 8 cores. Whether you get the high-end or low-end of that range really depends on the workload, specifically when more than 4 threads are needed. If the workload is "bursty" (ie: most applications & games) then you will likely get the highest possible frequency, but if the workload is a static 100% load (which is rare outside of stress test apps) that is just hammering the cores, then expect the lower-end. Either way, Zambezi's Turbo CORE seems to hold the turbo frequency better and longer than the previous ititeration.

Are there any worthwhile performance gains? Let's find out:

As you can see, the gains are quite evident when it comes to lightly-threaded workloads, with a performance increase of about 14-15%. This is pretty much in-line with the 17% frequency boost that Turbo Max provides. However, in very highly-threaded applications the performance difference ranges from none at all to a little under 5%. Thankfully, if you do encounter a highly threaded workload, you do have eight highly clocked cores are your disposal.

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