How to Flash Ninphetamin3 Kernel on Galaxy S3

First and foremost, make sure you are using a stock based ROM on your phone. This kernel will NOT work with AOSP ROMs such as CM9 or AOKP.
Download and install the software Kies on your computer, which will install the necessary drivers for the phone.
Download KiesYou can also use the Galaxy S3 toolkit → here to install only the drivers. Also, if you install Kies, make sure it is not actively running even in the taskbar or it may interfere with the flashing process.
Download the kernel:
Download Kernel | Filename: ninphetamin3-release-1.1.0.tar.md5
Download the Odin PC software. If you are new to this, Odin is what is used to flash stuff – firmwares, kernels, etc. – on Samsung phones. We’ll use Odin to flash the firmware file obtained in step 3.
Download Odin3 v3.04 | Filename: Odin3_v3.04.zip
Extract the contents of the Odin3_v3.04.zip file to a folder on your computer.
Now, turn off your Galaxy S3 and wait for it to shut down completely.
Then, put the phone into download mode. To do so, press and hold these keys together: Volume Down + Home + Power till the screen turns on. Then press Volume Up to continue to enter download mode.
Open Odin by double-clicking on the Odin3 v3.04.exe file obtained in step 5 after extracting Odin3_v3.04.zip.
Important! Connect your phone to PC now. You should get the message “Added !!” under Odin’s message box in the bottom left.
If you don’t get this message, make sure you installed drivers correctly (using Kies or directly) as given in step 2. If it still doesn’t work, try changing to another USB port on the computer and also use the USB ports on the back if you have a desktop PC.
Click on the PDA button in Odin, then browse to and select the ninphetamin3-release-1.1.0.tar.md5 file obtained in step 3 above.
Important! Do not make any other changes in Odin except selecting the required files as given in step 10. Leave all other options as they are. Make sure Re-Partition check box is not selected.
Now, click the Start button to start flashing the kernel on your phone. When the flashing is complete and is successful, you’ll get a PASS message (with green background) in the left-most box at the very top of the Odin, and the phone will automatically reboot. When you see the Samsung logo, you can safely unplug the cable.
What do if Odin gets stuck or doesn’t do anything: If ODIN gets stuck on setup connection or at any stage of this process after you’ve hit the Start button, and doesn’t seem to be doing anything, or if upon completion of the process you get a FAIL message (with red background) in ODIN, do this: disconnect the phone from the PC, close ODIN, remove battery for 4-5 seconds, re-insert it, turn phone on in Download mode again, and do the procedure again from Step 8.
After the phone reboots, you can overclock the processor using an app such as SetCPU orNo-Frills CPU Control or any similar app. Again, be careful and test different overclock frequencies to find the most stable overclock.

The Ninphetamin3 kernel is now installed on your Galaxy S3, which will let you overclock the processor inside up to 1.8 GHz. Try it out, and let us know how high your device is able to overclock and whether you notice any performance improvements, in the comments below.