Step Two: Flashing a Custom Kernel
Custom kernels are the key to overclocking, but they actually do a lot more than simply allow you to overclock. Custom kernels also often have extra features that improve or modify various aspects of your phone. Some kernels have deep sleep states for additional power savings, others allow a device’s capacitive buttons to light up in place of a notification light, and some have all of the features and modifications combined. As a result, there can be an awful lot of different kernels to choose from.
But before we get ahead of ourselves, you might want some information on just what exactly a kernel is. In the briefest of explanations, a kernel is the core of an operating system. It manages the system’s hardware to best serve the needs of the applications. Because Android is an open source platform, kernel code is available to the public, and because Android is a Linux based operating system, there are already thousands of developers familiar with kernel creation.
Kernels handle things like CPU speeds and voltages, and a custom kernel can have a modified CPU table that allows for speeds well beyond the CPU’s original specifications. To start overclocking, all you need is an overclocking-enabled kernel, but it’s important to choose the right one.
Finding the right Kernel
The best place to start your search for a custom kernel is on the XDA Developers Forums, specifically the forum for your particular device. Which features a kernel offers are all a matter of personal preference; however, it is absolutely crucial that the kernel you choose is compatible not only with your specific device model, but the version of Android that you have installed as well. Kernels are also often separated into those meant for stock ROMs, and those meant for custom ROMs.
If you are unsure if a kernel is compatible with your device, ask before attempting to install it. Flashing the wrong kernel will prevent your device from booting properly and can even permanently brick it.
Flashing a Custom Kernel
Once you’ve confirmed that the kernel you’ve selected is compatible with your device and its software configuration, flashing it is quite simple.
Start by booting into your custom recovery mode, such as with the button combo while powering on or using the ROM Manager app. If you haven’t already, it is wise to create a “nandroid backup.” This will back up everything currently on your phone except for an SD card.
A nandroid backup is created through the custom recovery mode by selecting “backup and restore” and then selecting “backup.” This step can take several minutes dependent on how much you have installed on your device.
When it’s finished, connect your phone to your computer via USB (if you haven’t already) and select “mounts and storage” followed by “mount USB storage.” Then, on your computer, open your phone’s storage folder and copy the “clockworkmod” folder to a safe place. You can restore your phone to its current state at any time by copying that folder back to your phone, booting into recovery mode, selecting “backup and restore” followed by “restore” and choosing the appropriate date.
While your phone is still connected to your computer, download and copy your kernel file to your device. It will be a .ZIP file, but do not unzip it.
With the kernel file on your phone and the backup folder in a safe place, select “Unmount” followed by “Go Back” to get to the main recovery menu.
As an optional but highly recommended step, select “wipe cache partition.” This will not erase any of your data but will remove any cached information that may conflict with your new kernel.
Lastly, select “install zip from sdcard” followed by “choose zip from sdcard.” Find the kernel file you copied to your phone, select it, and choose “Yes” to start the flashing process. This will take several seconds to a minute. Do NOT restart the phone or pull the battery during this part.
Once flashing is complete, select “reboot system now.” The first boot can take up to 10 minutes while applications are optimized for the new kernel. With the new kernel installed, you’re just about ready to start overclocking.