Chosen Solution
I have a 2011 MacBook Pro that I know has GPU issues, but it will only boot half way and then stops. I just installed OS-X on this drive using another MacBook and it worked on that one. Could the drive cable be bad? Also is there any way to fix the GPU without disabling it? It also does the same when booting from a known good Yosemite USB thumb drive. Thanks!
Sadly you have a bad GPU chip and the chip is no longer available from AMD. Some board repair shops may still have them but the cost of mounting a new chip given the value of the system makes this iffy. Some people have tried heating the chip to revive it. Sorry to say this is nothing more than a last gasp of a dyeing system. You see, the design of these chips is what did them in, as well as us pushing them too far running apps that just where too much for them so the system overheats causing the GPU to breakdown faster. We fail to realize the timeframe these older systems were designed in and what great strides in apps over the last five or so years that these systems just can’t handle. You could disable the dedicated GPU and use it with its Intel graphics engine while this will work it won’t be at the level this system was able to run. The fact your internal or thumb drive won’t boot up is all related! As the POST is whats hanging. To prove this you can boot up under Target Disk Mode (you’ll see the FireWire/Thunderbolt Icon on the screen) then reboot and this time run your system in Safe mode. At that point you are running on the Intel GPU if you can get over the POST condition. Sometimes I had to do a SMC reset to get this to work as well. Reference: Mac startup key combinations
Sounds like your MacBook Pro suffered exactly the same issue as mine. Mine got the booting problem solved but at the cost of the battery as it was not charging at all. Try starting the MacBook Pro without a battery, see if it can boot to the login screen. For the GPU, you better off finding a proper replacement chip that Apple issued for the problem, since reballing the old chip may fix the problem, but temporarily, even with leaded solder.
