While one can get almost any info on most of AMD's x86_64 platforms ( and even there many parts seem to be sorely missing- above all for APUs) but with GPUs available literature reads as informatively as a chinese phonebook in Bulgaria.
Abstraction packets like OpenCL SDK are nice, but thing with abstractions is, they are helpfull only when "app programmer" is thinking along the same wavelength as the abstraction creator AND when abstraction creator correctly predicted all user needs and catered for them.
But GPU is not CPU and GPU computing is not nearly as mature as CPU computing. Also, while it is nice to be able to write program wothout concern for every physical contraint and time delay, many times it is important to be able to be "Close to the Metal".
Shader program are not multimegabyte monsters. Often times they are on the scale of what we have used to routinely write in assembly for 8051, PIC and many other microcontrollers. Such code could be mantained and polished by hand or through the use of some other abstraction.
It would be very nice to know MUCH more about internals. I don't see wha is thuis so closely guarded secret. It's non-disclosure will only hurt honest developers since competition already has and uses decompilers, signal analyzers and whatnot to get the info they need. Only ones left without are ones that can't afford to screw around with hacking.
Is there a way for me to get really honest, detailed and explained info on AMD GPUs ? Do I need to sell my soul to the devil (NDA) ? Is my soul even worth that much ? I am primarily interested in APU internals ( especially latest and ones /Steamroller + GCN /that are comming soon), but GPUs would be fine also and even IGP ( within RS780 etc).
Have you gone through the documentation we provide to support open source driver development ?
Start at http://www.x.org/wiki/RadeonFeature and scroll down to the end.
The "AMD R6xx+ Acceleration" gives you an overview of how commands & data get into the GPU, and the ISA guides for each generation give you the details of the instruction set used for shader or compute programs.