"The real problem is that any modern x86 processor including the Pentium III can execute multiple instructions at once. So it's not like emulating a Z80 doing one instruction at a time. The actual algorithm and how x86 does this is undocumented and still unknown. In short, the Xbox's CPU can be emulated, but not accurately."
How is that relevant? Is there any code compiled for the Xbox that actually relies on how the P3 handles microops and pipelines things and all that? Cause if your argument is "X=A+B+C+D" might have several different ways of happening, the answer is that it doesn't matter. So I'm not sure why the author bring this up.
The Wii chip is also OOO but Dolphin seems to do a fantastic job.
Perhaps they know the PowerPC's algorithm for performing out of order execution? It might have been available for a long time, or have been shared to the public after IBM started opening up the Power architecture since 2004.
CPUs (x86 or PPC) only do out-of-order execution when it is provably the case that it doesn't matter. The result of running any given sequence of instructions in lock-step, or out-of-order should be exactly the same. If not, you found a CPU bug!
That said, timing matters in these tight inner loops, and that is where the details of the CPU pipeline matter, with respect to emulators. How many nanoseconds would it have taken for the emulated CPU to execute those instructions? That requires knowledge of how the CPU works. And sometimes, unfortunately, game code stupidly depends on these details.
With newer-gen high-level consoles and emulators, is that really the case? Having cycle/instruction accurate emulation only seems to be an issue for older consoles (PS2 and before?) where programmers actually relied on all sorts of things to eek out every cycle's worth.
How is that relevant? Is there any code compiled for the Xbox that actually relies on how the P3 handles microops and pipelines things and all that? Cause if your argument is "X=A+B+C+D" might have several different ways of happening, the answer is that it doesn't matter. So I'm not sure why the author bring this up.
The Wii chip is also OOO but Dolphin seems to do a fantastic job.