Looking at slide 29 of the HSA presentation, it looks like the Khronos APIs ( OpenGL, EGL, OpenVG, OpenGL ES, OpenCL etc.) will be implemented in terms of HSA. If that's true, I would take that to mean that a programmer might also be able to program directly with the HSA "language" as well... Or will it be a nice protocol similar to OpenGL et al. The mind runs wild.
C code, python code, machine code... all these things are software code that can be programmed and modified.
With x86 you have what is called the ISA.
ISA can be seen the API for your CPU. You may have heard of the CISC versus RISC processors and which is better or whatever. While x86 is a CISC instruction set, but all modern processors are in fact RISC processors. Even your x86-64 CPUs are all RISC processor cores.
How it works is that Intel and AMD have a hardware-based abstraction layer that takes the CISC instructions and transforms them into RISC code that is what is actually executed. The so-called 'x86-tax' in the ARM versus x86 wars refers to the complex set of transistors that perform this function. This is just about the only reason the Atom processor hasn't displaced ARM on phones yet.
Well this ISA is very important. This why code compiled for ancient 486 processors can be made to still work today.
But we have a problem......
Modern processors, due to Moore's Law, is ever increasing in complexity. Every 18 months or so they can double in complexity while not increasing in price.
Unfortunately there is a limit on useful it is to increase the complexity of a single processor core to make it faster. We saw this with the Pentium-4 netburst architecture. It tried to use long pipelines to go faster, but it ended up being beaten by AMD who took a different approach.
So now instead of making the processor more complex we just add more processor cores. 2 cores. 4 cores. 8 cores. 16 cores. That means we can do more and more work on a single machine.
But we still have a problem....
There is a limit on how useful this approach is. On servers people have taken advantage of this through virtualization and such things, but on desktops and laptops a 32 core system isn't really going to be much faster then a 4 or 6 core system running the same type of cores at the same clock speeds. There just isn't a whole lot going on except for the main thing that the person is paying attention too. And threaded programming isn't the panacea that most people seem to think it is.
What is the solution to making things go faster/more efficient then?
Well you use different types of cores for different things. Different processors are better at different things. So if you have multiple processors of different types then you can go faster and save more battery.
This is why closed source drivers and non-disclosing GPU designs are such shit when it comes to general computing. The GPU is ceasing to be a separate entity. It's not something you just add on to make games go faster or to make video smooth.
The GPU is one of those 'different cores' that you can integrate into your processor to make everything go faster.
But to be used on the GPU the software needs to be able to use it.
I think that this is what a big part of AMD's HSA is about.