I've had this laptop for about a day now and have decided to try Ubuntu on it and determine if I want to install it. I created a USB, it booted (Secure Boot was on, I tried with Secure Boot off to no effect), and then the problem occurred.
The screen turned off for a second, turned back on to a black screen, shut off again and turned back on with a dialogue box telling me that the system had to use low-graphics mode. I clicked OK, selected low-graphics mode from the menu and clicked OK. The screen switched to the boot messages and did not go any further than this. Ctrl+Alt+DEL started rebooting the laptop though.
I tried booting again, but this time I edited the boot options in GRUB to add
nomodeset. This time, the laptop only booted to a black screen. Ctrl+Alt+F2 took me to a prompt, I tried
startx from there, but X didn't start, complaining that it wanted kernel mode setting back.
I can not seem to find any option to disable one graphics chip or the other in the UEFI setup menus.
Laptop : HP Pavilion 15-E004AU.
The CPU : AMD A6-4400M APU with Radeon(tm) HD Graphics
The graphics chip : AMD Radeon HD 7520G + 8670M Dual Graphics.
The Ubuntu version : 13.10, 64 bit.
EDIT: I tried 12.04.3 LTS, it managed to bring the desktop up. There are severe graphics glitches after about two minutes though.