I have created an USB installer on an external HDD with clover on it (the last version gives here http://www.insanelym...1010-dp1-usb/).
The computer boot well until the sound assertion, then i have to wait 1 mn to go with a white screen and an apple (with a progress bar) and after nothing. i have wait 30mn but nothing happened.
I have an HD6870 and B75M DGS. But The clover i'm using work well if I used it to start on a 2nd HDD with Yosemite (that I install with my MBPr)