Intel Haswell CPU 1160

Intel finds specialized TSX enterprise bug on Haswell, Broadwell CPUs

Intel has discovered a bug in how its current “Haswell” and upcoming “Broadwell” Core microprocessors handle a specialized function known as Transactional Synchronized eXtensions (TSX) and has turned that feature off in the affected chips, the company confirmed Wednesday.

The technology was primarily used by transactional databases, and only a subset of the current “Haswell” Core chips even have TSX enabled at all, including some of the Core i5 and Core i7 chips, according to an Intel product matrix. (A deeply technical explanation of TSX can be found on the Intel website.)

However, the problem for those affected is the bug has been hard-coded into both the current generation of Haswell chips and the first shipments of Broadwell chips already delivered to hardware OEMs, according to Intel. In response, Intel has issued a software “microcode update,” a patch that simply turns TSX off rather than fixing it. 

“We have addressed the TSX issue with the release of a microcode update that disables TSX on current steppings of the affected Haswell and Broadwell products,” an Intel spokesman said in a statement. “Longer term, Intel is committed to correcting the issues with TSX and enabling the feature on future processors.”

The flaw was apparently discovered by an external Intel developer, according to The Tech Report. Intel has issued a formal bug report for the problem, noting that “under a complex set of internal timing conditions and system events, software using the Intel TSX (Transactional Synchronization Extensions) instructions may result in unpredictable system behavior.”

Of little concern for PC users

Dean McCarron, a microprocessor analyst with Mercury Research, described TSX as a memory-locking technology for transactional databases, one that’s confined to the server market. “If consumers are going to be impacted, then they’re a very, very sophisticated breed of user,” he said.

The type of customers using a transactional database are very sophisticated about what they try and what they buy, McCarron added. “The downside of that is that they’re probably the most sensitive to that kind of issue, which is why it’s getting a bit more publicity than it normally would.”

Intel typically finds and publishes hundreds of bugs—known as “erratum"—some of which only crop up under certain conditions or in certain products. Of those, a few affect consumers at large: in 2011, for example, a bug plagued Intel’s “Cougar Point” chipset, and a bug within its SSD 320 drives could cause them to unexpectedly fail.

Finally, there was the infamous Pentium bug, or “FDIV bug,” which caused the Intel Pentium to report the wrong answer when performing certain specific mathematical calculations. Intel initially waved away the reports, then later recalled all affected processors after a public backlash. Intel is not recalling any of the chips affected by the TSX bug at the moment, however.

Within the enterprise space, the TSX bug could conceivably be somewhat more serious. At present, however, it appears to be a relative non-issue for the PC community.

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