The WinXP 64-bit is not only AMD 64. Inq stated, as well as Microsoft for sure, that it will have among the 64-bit support, SUPPORT for AMD64. Doesn't mean at all it is based on AMD64.
You're right, that doesn't mean it is based on AMD64. Actually, AMD64 was more based on the guidelines set by Microsoft, and thus Universities developing the standard, than the other way around.
However, Microsoft had to have a 64bit platform to do testing and developement on. They certainly didn't do it on the IA64 platform, so they had to have been using AMD64 emulators and AMD64 processors (unless Intel already had their 64bit architecture finished and in Microsoft's hands). While Microsoft may have a wider 64bit guideline than AMD64, any 64bit processor coming out must be x86 compliant. I doubt you could be compatible with MS guidelines using a non-x86 architecture.
Intel could try to bully Microsoft into making a separate code path for their processors. Then we would run into many problems with compatibility. From a developers standpoint, it is much easier for a gamer maker to make separate code paths than for an OS maker to do so. They game maker doesn't have to worry about programs running on top of it. Microsoft would sooner market two separate OS's than try to support two code paths and resolve all of the issues that come up with other software companies.
Assuming Microsoft was as weak as AMD, Intel could bully them into making that separate version of windows and letting the other die out. However, we must not forget that Microsoft owns more of the desktop market than Intel does. The average consumer cares more about Microsoft than Intel and thus puts Microsoft in the position of power in the desktop arena. Therefore, Intels desktop CPUs will comply with Microsoft's specifications (x86) or they will find another OS to champion.
Because of this, I can only see Intel making an AMD64 compliant design, with further extensions to make their processor "supperior". Kinda like the 3DNow and SSE.
It'll be easier fr everyone, including Intel, to make their processor compliant with AMD64. In the future, when all software is running 64bit, they could introduce a new pure 64bit design with ease, in comparison to doing it now. By then, processors will be so fast that 32bit emulation will preform about the same as real 32bit does now.
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