RehabMan,
In advance I just want to thank you for your help and knowledgeability. I'm writing right now from my XPS 13 (2015|9343, 1080p non-touch), with full graphics acceleration, working battery identifier (your kext), webcam, wi-fi, touchpad multitouch, and sound working. I narrowed down what I think might be the cause of the flashing glitch/graphics failure, because they disappeared after I disabled C-States in the laptop BIOS. I'm still not sure my SMBIOS is configured correctly, I've quoted that section of my Clover bootloader below if you could check it for me.
I still lack PM on the processor and it does not identify correctly in "About This Mac", but I'm content with living with that issue.
If this build remains stable over the next few days I'll make a write-up on how I did it and upload my bootloader folder!
Code:
<key>SMBIOS</key> <dict>
<key>BiosReleaseDate</key>
<string>03/24/2015</string>
<key>BiosVendor</key>
<string>Apple Inc.</string>
<key>BiosVersion</key>
<string>MBP121.88Z.0167.B02.1503241251</string>
<key>Board-ID</key>
<string>Mac-E43C1C25D4880AD6</string>
<key>BoardManufacturer</key>
<string>Apple Inc.</string>
<key>BoardType</key>
<integer>10</integer>
<key>ChassisAssetTag</key>
<string>MacBook-Aluminum</string>
<key>ChassisManufacturer</key>
<string>Apple Inc.</string>
<key>ChassisType</key>
<string>08</string>
<key>Family</key>
<string>MacBook Pro</string>
<key>Manufacturer</key>
<string>Apple Inc.</string>
<key>Mobile</key>
<true/>
<key>ProductName</key>
<string>MacBookPro12,1</string>
<key>SerialNumber</key>
<string>C02XXXXXFVH3</string> ((obfuscated))
<key>Trust</key>
<false/>
<key>Version</key>
<string>1.0</string>
</dict>