AMD Phenom II X6 1055T & 1090T Six-Core Processors Review

Author: MAC
Date: April 26, 2010
Product Name: AMD Phenom II X6 1055T & 1090T Processors
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Feature Test: Turbo CORE Technology

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 the supported operating frequencies and voltages that the processor can switch between in order to modulate power consumption and lower heat output. These states are controlled by the ACPI function in the operating system depending on idle/load status. Processors can move in and out of these P-states very quickly, seamlessly to the user. The lower the P-state number, the higher the processor speed. P1 in this chart is the 'stock' frequency.

With the Phenom II X6 processors, AMD have implemented a new P-state, Turbo/P0, that is only switched to under single, dual, or triple-threaded workloads. In those cases, the 3 or 4 or 5 idle cores go into a low-frequency halt state (800Mhz), the voltage is increased for across all of the cores, and the additional power and thermal headroom is used to increase the frequency of the 1 or 2 or 3 cores that are currently loaded. If your workload requires four or more cores, the processor will simply run at default clock speeds.

Although great to have one way or another, we could definitely make the case that AMD's Turbo implementation is at least one generation behind Intel's. With Intel Turbo Boost, the unused cores are shut off, this means that they aren't drawing any power whatsoever. As a result, a larger percentage of power envelope can used allocated towards boosting the loaded cores. AMD's solution merely put the cores into idle, in which case they are still drawing power, thus reducing the theoretical Turbo capabilities of chip.This is arguably why AMD can't have the Turbo feature enabled on more than 3 cores.

Nevertheless, here is how the Turbo CORE implementation works in real-time:

1055T on the left, 1090T on the right - Click on image to enlarge

The 1055T 2.8Ghz will Turbo up to 3.3Ghz when up to 3 cores are loaded, the 1090T 3.2Ghz will Turbo up to 3.6Ghz when up to 3 cores are loaded. Why only enable Turbo on 3 cores? Well as mentioned above that was a likely decided based on thermal and power considerations, since they do have to say within that 125W power envelope. Having said that, we would have liked to see a mid-way Turbo point for four-threaded workloads.

Since this is a performance-oriented feature, let's see how the Turbo CORE function affects real applications:

As you can see there are worthwhile gains in apps that use less than four-cores, but that's becoming less and less common nowadays. Thankfully, if you do encounter a highly threaded application you do have those wonderful six cores are your disposal. On a side note, we do have to point out that we did encounter a few occasions where the Turbo performance was not as high as expected. We suspect that this issue was caused by the operating system shifting the workload from core-to-core, but that's just conjecture at this point.

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