With the initial Linux tests of the AMD Athlon 5150 / 5350 & Sempron 2650 / 3850 out of the way, I ran some basic overclocking tests on all four of these week-old AM1 APUs.
To not much surprise given these are $60 USD parts and under, there isn't much to squeeze out of these Kabini APUs with Jaguar processor cores. Many AM1 motherboards reportedly are not even offering any overclocking options from within their UEFI setup area. Fortunately, the ASUS AM1I-A motherboard that I've been using for many of these AM1 Linux benchmarks, offers basic overclocking support.
The ASUS UEFI BIOS Utility for the AM1I-A mini-ITX motherboard allows adjusting the APU frequency, memory frequency, CPU ratio/multiplier, north bridge frequency, DRAM timings, APU voltage, and the DRAM voltage. Regarding the adjusting the multiplier on the APUs, only the AMD Athlon 5350 and Sempron 2650 that had a multiplier that could be increased beyond its default value. For all four of the APUs with the basic overclocking, when attempting to adjust the APU frequency past 105MHz, regardless of voltage, the system would become unstable.
AMD Sempron 2650 - The dual-core APU clocked at 1.45GHz by default (100 x 14.5) could be bumped to 1.50GHz with the maximum multiplier value of 15. Increasing the APU frequency to 105MHz yielded a 1.575GHz clock speed for the two AMD Jaguar cores. Bumping the APU frequency also led the system memory to running at DDR3-1399MHz (the Sempron 2650 is capped to DDR3-1333MHz over DDR3-1600MHz with the higher-end AM1 APUs.)
AMD Sempron 3850 - With not being able to increase the multiplier any higher, the quad-core 1.30GHz APU could just ramp up to 1.365GHz when increasing the CPU ratio to 105MHz and the AMD DDR3 system memory was then running at DDR3-1680MHz. Pushing past a 105MHz ratio -- as with the other APUs -- led to stability issues.
AMD Athlon 5150 - The multiplier on the Athlon 5150, which stock runs at 1.60GHz for the quad-core APU, also couldn't be increased and thus when going with the 105MHz APU frequency led to a 1.68GHz frequency for the APU and system memory.
AMD Athlon 5350 - Lastly, for the highest-end AM1 APU right now, the Athlon 5350 (2.05GHz quad-core), its ratio could be bumped from 20.5 to 21. With that bump plus a 105MHz frequency yielded a clock speed of 2.205GHz and DDR3-1680MHz for the system memory.