permanently turn off discrete graphics chip on macbook pro

My trusty 2011 mbp discrete graphics chip has died. It wouldn't boot- just gets to a point in the boot and shows bad lines on the screen and hangs. It even hangs on a USB recovery disk so it isn't the internal drive/settings.

I put the mbp into target disk mode and moved /System/Library/Extensions/AMD6000Controller.kext folder, cleared the kernel caches and restarted - and the computer works! Yay, but now the screen is really laggy - and is not usable. Wondered if there are tweaks I can do to the the AMD6000Controller.kext info.plist that will cause the integrated graphics chip to always be used?

I called apple, and even though the macbook was 5 years out of warranty, and the warranty extension program had finished end 2016, they still honoured the warranty. So i got a new logic board for free. Happy days. ;-)