An XDA user has released custom kernel for the exynos-powered Samsung Galaxy Alpha that allows you to easily overclock or under clock. You can change clock frequencies of A7 core to 200-1800 and A15’s core to 200-2000. To change clock speeds easily we recommend installing Synapse from play store.
Under clocking a processor increases the battery life while overclocking improves performance. We tested this Galaxy Alpha custom kernel at 2.0 GHz and did not notice any extra heat. Phone remained stable too. We recommend 500-1800 MHz for a15 cores and 200-1800 MHz for A7.
It shall be noted that it is not a firmware or a ROM. This is a kernel meant to be flashed over a stock ROM. Here is the screenshot of results achieved by overclocking. As you can see it surpassed the mighty Galaxy Note 4 in the AnTuTu Benchmark.