The Raspberry Pi Foundation released a new Raspbian SD card image yesterday with some interesting new features including dynamic overclocking. I had the July Raspbian image on an SD card which I already setup with everything I need to do a demo, so I didn't really want to have to startover with a fresh image. Therefore, I decided to give the upgrade process a try:
UPDATE: If you just want overclocking and not a full update of all packages, then asb suggests just doing sudo apt-get update && sudo apt-get install raspberrypi* raspi-config
1) From LXTerminal, I was able to upgrade the installed software packages via:
sudo apt-get update
sudo apt-get upgrade
You'll need to be connected to the Internet and beware that the second command, upgrade, took well over a hour to complete.
2) The next step is to upgrade the firmware by using the rpi-update utility. I didn't already have this utility, so I downloaded it via the instructions on the GitHub:
sudo wget http://goo.gl/1BOfJ -O /usr/bin/rpi-update
sudo chmod +x /usr/bin/rpi-update
It complained that git wasn't installed when I first attempted to run it, so I had to install git:
sudo apt-get install git
I was finally able to rpi-update after that which completed successfully stating that it had downloaded and installed the firmware:
3) Finally I updated the raspi-config utiltiy so that I would have the new overclocking menu option. To start the utility, type:
Then select the Update option:
After the update is complete, you'll find a new menu option in raspi-config when running it again: overclocking!
I selected Turbo and then allowed raspi-config to reboot the system.
4) Upon the system rebooting, I verified I had an upgraded kernel:
pi@raspberrypi ~ $ uname -a
Linux raspberrypi 3.2.27+ #160 PREEMPT Mon Sep 17 23:18:42 BST 2012 armv6l GNU/Linux
I was pleseantly suprised to see it's now a Linux 3.2 kernel instead of 3.1 as it previously had been.
5) I was eager to give the overclocking a spin. The CPU frequency is dynamically overclocked when the system activity warrants it (and internal chip temperature is low enough to be safe). In order to tell when the overclocking was happening, I wrote quick loop in the shell to log the current CPU frequency every 5 seconds:
And then I played Quake for a bit. Sure enough, this triggered the Pi to kick up to 1GHz for a period of time as my log revealed:
I also observed that the CPU would increase to 1GHz often when using the Midori web browser, too.
NOTE: there are few other optional upgrade tasks that you can do to completely replicate the new image. These are documented in this thread: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=66&t=17788&p=176847