Hey,   go to the BIOS Setting, then Display and disable the "Hybrid Graphics". After your Deployment you can enable it back. It's just an workaround, but for me it helped to install every Precision 7670 Devices which I have here. 
We have recently received an order of Precision 7670 laptops and are unable to get any of them to boot to Windows PE. We use MDT to deploy workstation to our users in our organization and while the laptop will load the LiteTouch.wim file, all that happens afterwards is a black screen with the Dell logo. I have spent hours trying to find if there is a solution to fix this issue.  I have the latest driver packs for WinPE and for this model, the boot images are completely rebuilt, and I have tried various driver settings to be included in the WIM file. I have also tried to downgrade the BIOS to a previous version to verify if it is not a BIOS/UEFI bug that Dell has not quality tested (this was the case with the Precision 3630 Tower BIOS/UEFI). Current BIOS/UEFI is 1.6.3, attempted to downgrade to 1.5.6 but received a "version not permitted"...I have allowed BIOS downgrade in the settings but why is this still locked out? Funny we also got a fresh order of the Precision 3660 towers and have not run into these issues with MDT deployment. Apparently other people are having similar issues running deployment for this laptop model as indicated below. [URL]  [URL]  Because this is a new model, I have not found much support or answers to why WinPE is not able to load or why MDT deployment is having issues. Hoping to get input on what settings, or drivers have been successful for MDT to deploy or for Dell to actually address a firmware quality issue on these expensive mobile workstations.
Precision 7670 - Not Starting Windows PE with MDT