Bug Causes Intel Skylake PCs to Freeze During Hyperthreading

Intel has confirmed that its Skylake processors can freeze during complex workloads. The bug, that “can freeze any system that has a Skylake processor,” was discovered by the Great Internet Mersenne Prime Search (GIMPS), which uses computers to identify new prime numbers. GIMPS was running its Prime95 software to find large prime numbers with the exponent size of 14,942,209, which, “after minutes or hours” crashed the system.

Intel forum user Henk_NL wrote, “the problem is related to hyperthreading and the use of CPUsupportsFMA3. Overclocking, underclocking or just running at stock speed does not influence the outcome of the program.”

Henk_NL also wrote a handy guide for masochists to use in order to replicate the freezing:

“Steps to freeze your Skylake system:

– Download and install Prime95 for Windows on a Skylake system from the website at http://www.mersenne.org/download/ (If you want to familiarize yourself with the software use the readme, a background in math will be helpful, but is not needed.)

– In the menu go to ‘Advanced | Test’ and fill in the number 14942209 in the box labeled ‘Exponent to test’

– Let the program run for some time and at some point, minutes or hours, the system will freeze.”

“It is my fear that like the infamous FDIV bug this issue will require a new stepping and a product recall, since this has security implications as well,” Henk_NL warned.

Intel’s official statement on it forum reads:

“Intel has identified an issue that potentially affects the 6th Gen Intel® Core family of products.  This issue only occurs under certain complex workload conditions, like those that may be encountered when running applications like Prime95.  In those cases, the processor may hang or cause unpredictable system behavior.  Intel has identified and released a fix and is working with external business partners to get the fix deployed through BIOS.”

There is no indication as to when the BIOS fix will be released.