Re: Intel vs AMD64

[Timothy Miller]

Nakajima, Jun wrote:
> Thanks for the clarification.
>
> Yes, "implementation specific" is one of the differences between IA-32e
> and AMD64, i.e. that behavior is architecturally defined on AMD64, but
> on IA-32e (as I posted): 
>   Near branch with 66H prefix:
>     As documented in PRM the behavior is implementation specific and
> should 
>     avoid using 66H prefix on near branches.


In other words, Intel's implementation deviates from the architecture as 
defined by AMD.  So it's not 100% compatible.  I just want this point to 
be clear.


If these sorts of branches are common enough (and I suspect they are), 
then this sort of deviation could have a notable code-size (and L1) 
impact on code which is compiled to be compatible with both implementations.

Why did Intel decide to do that?

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