That's just two pieces of the hardware; we're still miles away from emulating the Xbox kernel and all its calls (which differ from the NT way of doing things). I highly recommend reading
this description of the difficulties in creating a 3rd party Xbox 360 emulator.
ATI R500 emulation: The built-in ATI R500 chip was great for its time (circa 2005), but it's nowhere near the GPU performance we're used to these days; the Xbox 360 GPU was clocked at 500 MHz while today's Radeon 6950 puts out more than 800 MHz. Also, its overall architecture has improved by dozen-fold: where once 16 texture units were responsible for filling textures, you're now looking at 192 of these units. Memory bandwidth also doubled. The list goes on.
Emulating the 729 MHz PowerPC CPU of the Nintendo Wii requires fairly decent hardware to run at high resolutions. Imagine what it would take to emulate the Xbox 360's tri-core 3.2 GHz CPU. Yikes.
PowerPC emulation: The Xbox 360 is built on a
Xenon, a 64-bit PowerPC CPU with three physical cores that uses the RISC instruction set. Translating its instructions would require a compiler that'd take good care to correctly translate its caches, registers and so forth. x86 CPUs would have trouble emulating some of the Xbox CPU instructions fast enough, while in other cases they'd translate things too quickly. Simply put, it's like having a human language interpreter translating a speech in real-time, with no noticeable delay,
Microsoft Points card, while at the same time adapting to the speaker's erratic voice patterns and speeds.
But for the sake of the argument, let's just assume that Microsoft's Xbox and Windows team somehow worked their magic and created an emulator capable of overcoming all translation issues. Performance is still the biggest issue. Take the Wii hardware as an example: it runs on a PowerPC CPU and ATI GPU as well, but is not nearly as powerful as the 360. It took years for developers to create the
Dolphin emulator,
xbox 360 codes, which runs some (not even all!) Wii games and doesn't deliver smooth gameplay with anything less than a 3 GHz Core 2 Duo. And that's only emulating the puny little 729 MHz single-core PPC CPU that's built into the Wii. Compare that to the three-core 3.2 GHz architecture found in the Xbox 360. I can't even begin to imagine what kind of processors would be required for Xbox 360 games to be emulated flawlessly at 100 percent performance, but I suspect it's beyond what's available today (or even what'll be available in April 2012,
Cheap Microsoft Points, when
Windows 8 will reportedly hit the market).
Plus, you'd need at least a quad-core CPU to map all three physical cores of the Xbox 360 to your PC -- and don't forget that you've got Windows 8 and its background processes struggling for processor time, as well, so it'd be best to have at least a few spare cores.
So the only possible solution is emulation -- and this is where we run into big problems. Console emulators rank amongst the more complex pieces of software out there, as they need to translate custom console hardware instructions to x86. And while the Xbox runs a customized NT kernel and uses some form of DX9, its hardware is an entirely different story. An Xbox 360 emulator would need to struggle with:
So shouldn't it be fairly easy to emulate the R500 GPU? Unfortunately, things are not that easy. From what I've gathered, the R500 sports some unique instructions, such as
MEMEXPORT, that aren't available on desktop cards, and which are either hard or next to impossible to emulate in time.
The question is: Could Windows in theory run Xbox 360 games natively? No. Some Xbox Games are written in .NET/XNA, so I figure they could easily be JIT compiled, but the big commercial games (such as Gears of War or Call of Duty) would need to be recompiled and adapted in case the games contain hardware-specific code. And I'm not sure this is feasible at all.
I think it's all highly unlikely, unless Microsoft really put in the resources to create a fast and flawless emulator. It's very hard to pull off, so the question is: why would they?
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