So after much farting about with MXM graphics cards I've installed an Dell/AMD Firepro m6000 and finally got the internal LCD working without gradients.
Thanks to Amble and Deschutes for their posts here: http://www.insanelym...38#entry1977940
I had load hassle with wrong colours like in Amble's photo and gradients until I made an override for the panel's EDID using the AUO EDID Deschute's posted.
The M6700 is configured with an LP173WF1-TLB5 panel. Both the LP and AUO panel are 1920x1080.
Here are the relevant bits from Clovers config.plist:
And for the EDID override I created this file in /System/Library/Displays/Overrides/DisplayVendorID-30e4:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
Note that in the ATIConnectorsPatch the personality for the LVDS is 0200 0000 4000 0000 0901 0100 10 00 00 05. The encoder is 00 not 01. 01 gives an image, but with jittering, and sleep causes a black screen. Also the Hotplay IDs start at 00, didn't work starting at 01. Couldn't get the EDID override to work in Clover, don't know why.