AMD A8-3870K Llano APU Linux Overclocking

One of the first overclocks of the A8-3870K that was done simply was raising the multiplier from 30x to 35x while maintaining the 100MHz reference clock, which resulted in new APU running at 3.5GHz. That was very easy and always stable on the two different A75 motherboards tested. When running the A8-3870K between 3.6~3.7GHz using a variety of different multiplier/clock combinations and only a minor bump to the APU core voltage, the system was generally stable -- only a few crashes occurred in intense workloads like running Unigine Heaven or building out the Linux kernel multiple times. The highest multiplier I could run the A8-3870K was 38x while still POSTing but only sometimes being stable enough to boot Ubuntu.

At 3.9~4.0GHz when feeding the A8-3870K with over 1.5V and boosting the CPU NB VID control and trying various multiplier/clock combinations was when hitting the aforementioned issues. The APU was also running quite warm at this point with Thermalright air-cooling. The two motherboards that were used for testing was the Sapphire Pure Platinum A75 and a Gigabyte A75M-UD2H. Both were running the latest available BIOS releases. Note: when using the Pure Platinum A75 motherboard, on some boots when 4 x 4GB of DDR3 system memory was installed, only 12GB of memory would be detected.

The benchmarks in this article include the A8-3870K running at its stock speeds and then again at 3.5GHz, since 3.5~3.6GHz was the safe and stable area where all of the computationally intense benchmarks could finish without fault. I am still working on the A8-3870K overclocking a bit more and hope to have out more results later in the week.

The A8-3870K benchmarks were done with 4 x 4GB of Corsair Vengeance DDR3-1600MHz memory, Sapphire Pure Platinum A75 motherboard, OCZ Vertex 3 SATA 3.0 240GB SSD, and AMD Radeon HD 6950 Cayman graphics. On the software side was an Ubuntu 12.04 development snapshot with the Linux 3.2 kernel and the Catalyst Linux graphics driver. Thanks to the Llano APUs and various A75 motherboards already being on the market for several months, at least there is not much to worry about in the way of Linux compatibility issues.

The setup is nearly the same as what was used for the Intel Core i7 3960X "Sandy Bridge" Extreme Edition testing, so for these benchmarks the A8-3870K is being compared to the A8-3850 Llano, the AMD FX-8150 Bulldozer, and several Intel CPUs. The Intel CPUs included the Core i7 870, i7 920, i7 970, i7 990X, i5 2400S, i5 2500K, and i7 3960X.