Can't Install Sierra on P55-M UD2 i5 750

[rockappalla]

Hi everybody,
I changed to imac 14,2 and downloaded Sierra, made the USB drive with unibeast with the Legacy option but I can't boot,
I get stuck in this screen (never seen before) and can't go on installing,
any clues?
I've been running Yosemite for a long time with no troubles but I'd like to get Sierra ( I want to do a compleat HD wipe and start fresh)



Thanks for your help as always!

 

[rockappalla]

Tried to inject nvidia with unibeast but I'm still stuck at that screen, can't get past there...

 

[cmn699]

From the Grey screen in your initial post, try the following:

1. Choose Boot Maintenance Manager and hit Enter
2. Choose Boot From File and hit Enter
3. Choose USB and hit Enter
   
4. Choose EFI and hit Enter
5. Choose BOOT and hit Enter
6. Choose BOOTX64.efi and hit Enter

The problem leading to the above screen could be due to the USB port you had your USB installer inserted. Is that a working USB-2 or is that a USB 3 in which you have your Sierra USB Installer inserted?

 

[rockappalla]

Thank you, I tried your suggestion but no luck, I tried another USB thumbdrive and it worked (the first one was a bad 16gb drive, the one that worked is a Verbatim 8gb! I'm writing from my fresh Sierra installation!

Thanks again for the support!!!

 

[cmn699]

Glad you found the cause and fix.

 

[blu3_v2]

I'm writing from my fresh Sierra installation!

Would you mind attaching a copy of your config.plist file. I have a P55A-UD4P and have been unable to succesfully upgrade to Sierra. Keep getting kernel panics loading the installer. Thanks