How to Boot using AMD Radeon HD 7xxx:
The AMD Radeon HD 7xxx must be the secondary graphics device in your system in order to boot using Chimera/Chameleon without a boot error and gibberish text. This is because of the larger video BIOS size. You can work around this by having a second AMD PCIe card in your system, or if using a motherboard with integrated graphics, set it to display first. The primary graphics device will handle the boot portion, and allow the system to boot perfectly with full graphics acceleration.
For current Gigabyte motherboards with AMI UEFI, set these two settings for dual graphics.