About this guide
First and foremost, I am not responsible for the franco.Kernel. All the glory goes to Franco. Second, I am no expert. The information in this guide is based on information I have gathered online and my own experience. This guide is fallible.
I began using the franco.Kernel as soon as I got my Nexus 7 and really like it. However, the kernel offered a lot of options that I didn't use simply because I didn't know what they were or how to use them. I looked for a guide like this but could not find one. In hopes of helping others get started and to make a contribution to the forum community that has helped me so much, I present this humble attempt at a guide.
Any corrections, comments, or additions are welcome.
What is a kernel?
A kernel is the lowest level of software on your device. It acts as the go between for your device's hardware and the Android operating system. It controls functions like:
Why would I want a customized kernel?
Customized kernels provide modifications and (often) optimizations made by the kernels author. They often also allow for customization of some of your hardware's functions. The franco.Kernel provides these benefits in a very stable package and easy to use companion app.
What do you need
For the sake of this guide you will need:
-A rooted Nexus 7
-The paid franco.Kernel updater app installed
If you don't know what rooted means or how to do it, click here
We are using the paid app because it has more options, and because it supports the kernel author and his work. Pay to play friends.
Why grit? Because things can go wrong and they can go wrong bad. Worse case scenario is you brick your N7 or fry a processor from overclocking. That, most likely, won't happen. The possibility does exist, though. Then again so does the possibility of a meteor falling through your roof and smashing your N7. So be careful, make backups, and don't live in fear.
Do these things in this order:
1) Make a nandroid backup in your custom recovery. (ALWAYS backup before messing with things. ALWAYS.) If something goes wrong, you can always flash this backup and fix it.
2) Backup your stock kernel. Do this in the franco.Kernel app. Open the app, select ‘Kernel backup/restore’. Then touch ‘Backup’. Name your backup (like “Stock”) and touch ‘Clicky to backup’.
3)Flash the franco.Kernel using the app. Open the app, select ‘franco.Kernel updater’. It’ll ask if you’re sure, and you are.
If you are on 4.2 you will likely get a note at the bottom of the screen saying there is no 4.2 version available yet. There is, though. Download it here: and put it onto the folder named ‘kernel_backups’ on your N7. Then open the franco app and select ‘Kernel backup/restore’. Then “restore” (install) the file you just downloaded.
That’s it! You are now running Franco’s Kernel! Now let’s play with some options.
We’ll now go through the options that are presented for customization in the franco.Kernel app.
This is where having a custom kernel really gets neat. This is also where things can go wrong very quickly. Go slow and be careful. Also, don’t select any of the ‘Set on boot’ options until you know that what you just changed won’t cause problems.
This controls what speed your CPU runs at. The franco.Kernel does NOT overclock (run faster than stock). If you want to overclock, you will need a different kernel. The higher the frequency the faster your device runs, the more power it consumes, and the more heat it generates. Your processor scales, or changes frequencies, based on your governor and load (processing required by software).
Maximum CPU Frequency: This is the fastest your CPU will run at. 1300 Mhz is stock. By lowering this (called underclocking) you will have worse performance but better battery life. I recommend leaving it at 1300 Mhz.
Minimum CPU Frequency: This is the slowest your CPU will run at. 100 Mhz is stock. Raising this may increase performance, but will cause your CPU to idle high, wasting battery. I recommend leaving it at 100 Mhz
Current Governor: The governor is what controls how your CPU scales, or changes frequencies. To be efficient, most governors will idle low than scale up the CPU frequency as needed to run software. Each governor has benefits and drawbacks. I recommend using the ondemand, conservative, or interactive governors. The franco.Kernel offers the option of the following governors:
-interactive: The CPU scales to the max required frequency quickly, then scales down based on a timer in the kernel. This governor reduces frequency fluctuations and makes better use of the full range of frequencies the CPU offers. Can have better battery life than ondemand while providing similar performance. (Good trade off or performance and battery life)
-conservative: The CPU scales based on load, but is slow to scale up. This can create choppy performance, but provides better battery life. (Best choice for battery life)
-ondemand: For many kernels this is the stock governor. It scales up to the max frequency quickly, and scales back down slowly once the load is removed. The result is stable, fluid performance. However, by scaling up quickly and down slowly it can use more battery than other governors. Also, since it scales so quickly this governor can bounce between high and low frequencies, using power to do so. (Best choice for performance)
-powersave: The CPU is locked at the min frequency. The result is bad performance and great battery life.
-userspace: Allows the CPU frequency to be set by programs. This governor is beyond the scope of this guide.
-performance: The CPU is locked at the max frequency. Inefficient use of power, great performance, bad battery life.
Max GPU frequency: This is the fastest your GPU, the graphics chip, will run. Stock is 416Mhz. 484Mhz is a commonly used, stable, overclock speed. Again, higher speeds give better performance while producing more heat and eating battery life.
Max Companion Core Frequency: The tegra 3 in your N7 actually has five cores. The fifth, known as the companion core, is a lower frequency core used for light loads, like background tasks when your tablet is asleep. This is the fastest your companion core will run. Stock is 500Mhz. I haven’t heard of a benefit in over/underclocking the companion core. I recommend leaving it alone.
CPUQuiet Governor: This governor controls which of the CPU cores are available and when. This function is more or less unique to the Tegra 3. I haven’t played with these enough to make a recommendation.
-userspace: Beyond the scope of this guide.
-balanced: Cores are used based on CPU load. This will use more cores more often.
-runnable: Cores are used based runnable threads.
Set CPU settings on boot: If this box is unchecked all the changes made to the CPU speeds and governors will be reset upon rebooting. Leave this unchecked while you tinker. Once you have found a combo of the above options that works for you and is stable, check this box.
Governor Control: These options control the options within the governor and are beyond the scope of this guide.
Set Governor Control on boot: Since we didn’t make any changes we don’t need to worry about this.
Voltages: This controls the actual voltage flowing to the chip. There are a number of different reasons to change these voltages. Most are beyond the scope of this guide. Some stock kernels are not tailored to each individual device and provide a bit more current than needed. Lowering these voltages can provide better efficiency and battery life. I have reduced each value by 100 and still maintained stability. I recommend either leaving these values stock, or lowering them each by 100. DO NOT CHECK SET ON BOOT UNTIL YOU KNOW THE VOLTAGES YOU HAVE ENTERED ARE STABLE.
This guide is a work in progress. More to come!