Compiling your own Coreboot firmware for the Samsung Series 5 550 Chromebook

Okay, so, why would you want to do this? Well, in a nutshell, so your Chromebook pretty much behaves like a normal laptop i.e. no secure boot, will boot from any USB key, no more signing kernels and dd’ing them to obscure partitions, etc, etc. Before you start: It’s important to note this comes without any warranty, express or implied. If something goes wrong you will end up with a bricked Chromebook. If that happens you can purchase a Bus Pirate, Bus Pirate probe cable, and Pomona 5250 SOIC clip and get unbricking, as per my previous post. This will also make ChromeOS unbootable, so if you want to use ChromeOS at all, then don’t do this. The impatient and ill-resourced among you can scroll to the end for instructions on how to download and flash my Coreboot build, which again comes without any warranty and could bring hell and damnation upon your souls. There is now a patch which allows all 4 GB of RAM to be recognised, but it takes 5 seconds to reach the SeaBIOS prompt on a cold boot. Continue reading Compiling your own Coreboot firmware for the Samsung Series 5 550 Chromebook

Unbricking a Samsung Series 5 550 Chromebook

I recently tried to enable hardware VT extensions on my Chromebook using the Hacking VMX Support instructions on the ChromiumOS website and it didn’t work. Not only did it not work, I also had a second go at doing it, following the instructions verbatim (despite it leaving 3 “bad” instructions in there). This left me with an expensive paper-weight. This is how I’ve come to know how to unbrick the 550.

If you are here I’m assuming you are in a similar situation, and, hopefully, have a copy of the original firmware to hand, with which to unbrick. You will also need another laptop with a suitable Linux distro loaded, such as Ubuntu/Fedora, and have Flashrom installed. Onto parts. You will need a Bus Pirate, a Bus Pirate probe cable, and a Pomona 5250 8 pin SOIC clip. Don’t buy a 3M SOIC clip, the spring is far too strong, and it’s designed in such a way that the pins won’t make contact unless you “modify” it, see http://www.eevblog.com/forum/microcontrollers/3m-soic8-clip-waste-of-timemoney/msg33462/?PHPSESSID=e4d9fa7c85d3aee85d389405447973cc#msg33462

Continue reading Unbricking a Samsung Series 5 550 Chromebook

Neutering the “developer mode” screen on your Chromebook

I am the proud owner of two Chromebooks – one Samsung Series 3 ARM Chromebook and one Samsung 550 Chromebook. Like many serial tinkerers the frowny/sick developer “warning” screen, which you get if you want to overwrite the operating system having to enable developer mode, is more of a pain than anything, much as I recognise it is for security. Having to press CTRL + D at every boot, or wait 30 seconds and endure a loud, audible beep is not my idea of slick fun. Happily, it is possible to all but disable this screen, by rewriting the BIOS with the correct “flags”. This leaves the screen enabled, but it only displays for 2 seconds, and there is no beep. Unhappily, you have to physically open the Chromebook up and disable the inbuilt BIOS write protect to take advantage of this.

The procedure is a follows:

  • Open Chromebook and enable/disable write protect jumper
  • Read existing BIOS using flashrom
  • Write new BIOS file with correct flags using gbb_utility
  • Write new BIOS file to BIOS using flashrom

Continue reading Neutering the “developer mode” screen on your Chromebook