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Overclocking

AMD immediately gives us to understand that Lynx platform is not designed for overclocking fans. There are no Black Edition processor models with unlocked clock frequency multipliers among existing Llano APUs and there won’t ever be any. All processors in this family have locked multipliers for the processor and graphics core frequencies. Even AMD Overdrive utility doesn’t work with the new Socket FM1 processors.

However, it doesn’t eliminate the possibility of overclocking completely. Socket FM1 mainboards have the option to change the base clock generator frequency and you could use it to increase the processor clock frequency. However, it is important to keep in mind that this clock generator affects the frequencies of all system components equally. Therefore, if you increase the base clock by, say, 100 MHz above the nominal, you will simultaneously and proportionally overclock the processor, graphics core, memory and external system interfaces. The only multiplier in Llano that can actually be adjusted individually is the one for memory frequency and it can be set to 10.66x, 13.33x, 16.0x or 18.66x.

This is where the major problem emerges. The increase in the clock generator frequency quickly cases issues with SATA or USB devices detection and operation. And this (and not the processor) is the major factor limiting overclocking. According to the existing data, the maximum clock generator frequency when the system remains stable doesn’t exceed 120 MHz. However, as soon as you get past the 133 MHz threshold, most mainboards automatically adjust the multipliers used for external interface frequencies, so there might be one more operational interval somewhere between 133 and 150 MHz. Also note that the variety of clock generator frequencies, at which the system will remain stable during overclocking, may depend on the onboard controllers on each particular mainboard as well as on the configuration of the disk sub-system (for example, with some SSDs there might be fewer operational settings available).

We tried to overclock our A8-3800 processor on a Gigabyte GA-A75-D3H mainboard. The maximum base clock when our system remained stable was 146 MHz.

So, our APU in fact overclocked to 3.5 GHz, while the graphics core frequency increased proportionally from 600 MHz to 876 MHz. As for the memory, we used 13.33x multiplier and therefore could clock it as DDR3-1946. To ensure ongoing stability, we also increased the processor core voltage by 0.175 V.

Above described overclocking improved our system performance pretty significantly. According to 3DMark 11, the integrated graphics performance increased to the level of Radeon HD 6570, and the computational performance improved by 40%.

There is one unusual peculiarity about Socket FM1 overclocking. It turned out that the BIOS of some mainboards offers an option to increase the processor clock frequency multiplier and a separate option for the graphics core frequency. In reality these options do not work, but some diagnostic tools, such as CPU-Z take the multiplier values directly from the BIOS. So, Llano based systems produce all sorts of impressive screenshots showing how successfully Llano processors conquer the most outrageous heights. However, despite the readings in CPU-Z, the real Llano multiplier doesn’t change and the actual processor and graphics core frequencies depend only on the base clock.

 
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