a_wall_adapter wrote:
I opened the macbook pro and resoldered the gpu chip with a heat gun. Thanks for helping me troubleshoot. OS X 10.10.5 is runs well on this machine.
That is probably just a temporary fix at best. I've seen a YouTube video where a professional repair shop reflows the GPU. The thermal stress of the GPU getting hot, then cooling during use and sleeping & waking can be enough to break the solder connections again as the components expand & contract, plus with a laptop you may have the board flexing a bit as well if not on a solid surface.
It is possible to force the laptop to use the Intel GPU instead of the discrete GPU, but you will lose some functionality (may not matter for some people), however, the GPU failure may even get to the point where it will prevent the laptop from booting or even powering on.
https://gfx.io/
https://github.com/steveschow/gfxCardStatus
http://dosdude1.com/gpudisable/