Now I have to question if they have an easy time provided backward compatibility with high level API redirection "emulation" then why the hell didn't this come about much much sooner?
For more info on what I mean, look up the N64 emulator Ultra HLE (HLE stands for High Level Emulation). It was a revolutionary new type of emulation at the time if I'm not mistaken that was based on recognizing that as modern systems became more like PCs with first party provided operating systems and SDKs that forced you to go through API. Most performance critical work would passed into the SDK by well documented function calls eg glVertex4f(float x, float y, float z, float w ); that the first party had optimised library code written for and that all you had to do to emulate was translate the function calls with a simple wrapper (Facade and Decorator design patterns for the C++ OOP crowd). What non API specific user CPU code that remained was just basic non performance critical management and main loop code that made API and syscalls that could be easily interpreted or cross assembled and cached in native machine code on the host VM with a runtime JIT recompiler.
It's a very different paradigm for emulation compared to fetching and fast switching bytes at opcode level and writing a clock accurate fully simulated CPU. This latter is very resource intensive and inefficient and mostly unnecessary on systems that adhere to very strong OS and API models to do the majority of the high performance work.
Graphics is my specialty, not emulation (I was writing an OpenGL mini port in assembly language on the PS2 with full asynchronous DMAC chaining/VIF/VU1/GS even with multiple dynamically uploaded VU1 vertex programs based on the OpenGL state changes before other things came up in life.)
So I could be wrong, but I believe Ultra HLE was the first widely successful experiment in this type of high level emulation, and this HAS to be what 360->XBO is doing if it actually ends up being good. There is just no way these relatively slow AMD APUs are going to be performaning instruction level emulation of Xenon with any resemblence to native 360 performance.
