Transactional Synchronization Extensions, aka TSX, are a backwards compatible set of instructions which first appeared in some Haswell chips as a method to improve concurrency and multi-threadedness with as little work for the programmer as possible.  It was intended to improve the scaling of multi-threaded apps running on multi-core processors and has not yet been widely adopted.  The adoption has run into another hurdle, in some cases the use of TSX can cause critical software failures and as a result Intel will be disabling the instruction set via new BIOS/UEFI updates which will be pushed out soon.  If your software uses the new instruction set and you wish it to continue to do so you should avoid updating your motherboard BIOS/UEFI and ask your users to do the same.  You can read more about this bug/errata and other famous problems over at The Tech Report.

"The TSX instructions built into Intel's Haswell CPU cores haven't become widely used by everyday software just yet, but they promise to make certain types of multithreaded applications run much faster than they can today. Some of the savviest software developers are likely building TSX-enabled software right about now."

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