Every time you make any change to your system, IOReg is different. You can get the app from the Apple Developer/Xcode/Hardware Tools or IORegistryExplorer_v2.1.zip. For download, View Raw. IOReg/File/Save a Copy As...
got it, thank you. Very neat of you to host it on github!
For the HD7750 to display boot screen and get to the Desktop without tricks, you must boot from the EFI partition; Clover is ideal or Chameleon installed in EFI.
?? really? OMG, there is so much stuff I do not know. Scratch my head about the background why the boot source partition would make a difference. I'm comfortable with Clover by now so will switch over asap (the HDD is GPT formatted via Disk Utility and has the usual 200MB EFI up front).
For ANY Ati to (more or less fully) work in my Optiplexes, I always had to assign PCIRootUUID to 4 in the chameleon boot plist. I am not sure if Clover offers that key, too (or if it's not necessary with Clover).
Install the native AMD7000Contoller.kext and reply with IOReg.
I loaned the comp. to a friend an hour ago who's hackintosh's power supply blew up (literally). He took his to a shop today (to hopefully onlu swap the PSU), so I hope to have the Optiplex back soon (he does not exactly live around the corner so it might take a week before we can meet up again).
Once I'll have it back, I'll install Clover to 10.9.2 (and to EFI, too, then activate EFI), delete the three 10.8.3 kexts, and restore the original (unmodded) AMD7000Contoller.kext.
Which DSDT will you want me to use - the one with or the one without your 7750 mods?
Thank you for your expertise and guidance!