If your MBP doesn't get to white screen before shutting down while attempting to boot, hold down the option key and boot into recovery disk. Previously I had tried GFXbench to test it, and it went straight back to no vertical lines at boot. It got heated up a bit but no GPU issue so far. I even plugged it into a cinema display and played HD on youtube. I then I let it cool down completely, (in fact I put it outside on the balcony.)

I left it for about half an hour then switched it off by holding down the power button. If you boot and get vertical stripes > apple logo > white grey screen, let it run hot as the fans kick in block the keyboard from venting airflow or wrap the mbp closed in a blanket.

I followed these steps and got a workable fix:

Saw all the online action, the lawsuits etc… Hopefully apple will do a recall as it was bought by me for graphic intense tasks like video editing. I had similar non bootable problem with a MBP 17 inch (early 2011). gfxCardStatus (integrated only mode) is better in this respect so I use both and now I can say that the machine is very stable and reliable after all. After about a week of gpu-switch testing, however, I have to conclude that this solution has its drawbacks too: it works fine after shutdown (including abnormal or forced one), sleep, hibernation, but it does not prevent mbp from switching to dgpu on running graphic demanding apps such as googlemaps in browser. This saved me from frequent overheat shutdowns under blanket just to load the os (after overheat shutdown the system forcibly uses igpu but this state changes back after couple of boots so it becomes necessary to overheat again).

The application runs from terminal, reportedly uses the same code as gfxCardStatus but writes the setting into NVRAM(PRAM) so machine remains switched to internal GPU on next boot(s)/wake(s). Please note that only source code is there so Xcode is requred to compile the binary. It seems that I have found more reliable or permanent software solution allowing to permanently disable discrete GPU and use mbp (mine is Mbp 8.3 17i early 2011) with broken discrete GPU (failing to boot) than gfxCardStatus 1.8-2.2.1, namely.

What is the mac mini 2012 graphics card