So you just bought a Samsung Galaxy S4 that features octa-core processor. Too bad, there are not a lot of apps on the Play Store to take advantage of those extra cores. Do not worry as you can disable the extra cores to prolong battery runtimes of your phone. This is said to work just fine with the GT-i9500 – the octa core version of Galaxy S4. The other version, the GT-i9505, a k a, the US version does not support this hack (as it uses a different CPU and is quad core).
The hack requires you to have a rooted Galaxy S4 and ADB installed on your computer. All you need to do is locate the file called
/sys/power/cpucore_min_num_limit
..and change its value from 0 to say, 2. You can find more about it in this xda thread.
The phone still managed to get more than 10000 score in quadrant with 2 core active (see the picture given above). When not unclocked, the phone got 13185.