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What makes Xbox so hard to emulate?
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blueshogun96
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Post: #16
RE: What makes Xbox so hard to emulate?

Thanks for your feedback on this everyone, it really makes me feel that it was worth writing. As you can see, I've updated the article. See section 6.

Although, maybe I should have said this earlier, but there are many things that are simplified about Xbox that reduces it's difficulty to emulate. Things like the fact that all MMIO devices and ram are located on the same 4GB memory address space. For instance, if your executing an instruction in the top of ROM (0xFF000000 - 0xFFFFFFFF) and if that instruction doesn't directly change the EIP register, then it will roll over to 0x00000000 (which is the beginning of RAM) without generating an exception which makes my life a little easier. Also, the PCI bus layout is much more simplified and more definete than a PC's, making it easier to emulate. All of this Xbox hardware stuff is a real adventure Toungue


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shogun
07-20-2007 04:00 PM
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BigIg
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Post: #17
RE: What makes Xbox so hard to emulate?

blueshogun96 Wrote:

BigIg Wrote:
Just out of curiosity, is Xbox's CPU a Reduced Instruction Set or a standard P3?

Also, most consoles CPUs perform operations in the order they are received (at least 360/ps3), I'm assuming the Xbox isn't like that since it's just a modified P3?

-BigIg


It's a standard Coppermine Intel Pentium III processor with a halved L2 cache (128KB). It has MMX, SSE, etc. and it has a customized CPUID function. Also the INT instruction isn't supported afaik. I don't know how PowerPC emulates it's instructions, but x86 is capable of doing more than one instruction at a time.


Thanks for explaining. Smile


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07-20-2007 08:09 PM
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