Re: [ros-dev] RE: [ion] 19742: - ImplementRtlPrefectMemoryNonTemporal.Patch by Patrick Baggett<[e-mail]> and myself.

[Thomas Weidenmueller]

Alex Ionescu wrote:
>   If you have a "nop" by default, then your
> job is as follows:
>  - Detect support for the instruction
>  - If it's NOT supported, overwrite with ret.
>  Additionnally, the default state of the function is to WORK, which
>  fundamentally speaking is wrong because you're assuming that the
>  advanced functionality exists, and then you're disabling it. Since
>  you're trying to be safe, then the whole point is to protect from the
>  potential BSOD.
>  However, with a "ret" by default, you only overwrite with nop if the
>  instruction IS supported. Apart from the design issue itself, I think
>  the premise here is that more CPUs don't have the support for the
>  function, then the ones that do. 
That depends on whether the machine supports it or not, it's not a
general optimization. But you made it sound like one ;)

- Thomas