What are CMPXCHG16b, PrefetchW and LAHF/SAHF, given as additional requirements?

In the following link, expanding "What are the system requirements for Windows 8.1 Preview", under "Additional requirements to use certain features:", what are CMPXCHG16b, PrefetchW and LAHF/SAHF? And what CPUs support these features?
http://windows.microsoft.com/en-us/windows-8/preview-faq#
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In the following link, expanding "What are the system requirements for Windows 8.1 Preview", under "Additional requirements to use certain features:", what are CMPXCHG16b, PrefetchW and LAHF/SAHF? And what CPUs support these features?
http://windows.microsoft.com/en-us/windows-8/preview-faq#

CMPXCHG16b = Compare and Exchange Bytes.  Also known as CX16.  It is an extension of CMPXCHG8b or CX8.


PrefetchW = Prefetch data into caches.  It is the AMD equivalent to Intel's PREFETCHh instruction.  It is used to provide a performance boost to instructions in 64-bit mode.


LAHF/SAHF = Load Status Flags into Register AH/Store AH into Flags.  These instructions allow compatibility mode and legacy mode execution in 64-bit mode.  They are used in virtualization and floating-point condition handling in 64-bit mode.


Each of these improve speed of execution and add security features for elements of Windows and apps in 64-bit.


A lot of data regarding these and how they relate to software and security can be found on the Intel website, along with volumes of information, varying white papers, and specs of various processors and their capabilities on the Intel website, at the following:

http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html


Microsoft also has available a software utility that can help you determine what your processor is capable of doing and which instruction sets are available therein.  It is called Coreinfo, and can be downloaded here:  http://technet.microsoft.com/en-us/sysinternals/cc835722.aspx


Additional, detailed specs for Intel processors also can be found here:

http://www.cpu-world.com/sspec/index.html


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Thanks for the information. And, what are all the processors that support these features?

You are welcome.  I do not have a lot of time at this moment to gather up a complete list (I might a little later on) but the sources of data on Intel processors and features are here:


http://www.cpu-world.com/sspec/index.html


Select your processor to see whether it has the features, or run Microsoft's Sysinternals' Coreinfo to get a complete listing of features your processor has.

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Last updated May 16, 2020 Views 21,955 Applies to: