If not, the program gives up and reports a severe error to the user. Normally, this fixes the problem-if it was a temporary thing.
#Cpu stress test math and prime95 number failed code
If, while doing a real calculation, an error is detected, the code will rollback to a known good state and try again. So, checks were put in the code to try to detect them. Any mistake along the way can ruin the whole calculation. The code that detects the problem is there because the Mersenne primality caclulations on large numbers can take *months*. That method later brought the bug to wider attention at Intel.Īnd that pretty much gets us to today when the news has been breaking at bunches of tech sites. Meanwhile, a few MersenneForum community members joined the Intel forums to report the bug via that means. Only one made any headway-the security group was able to reproduce it on an older revision of the SkyLake microcode patch. Several personal contacts at Intel were attempted. Once it was determined not to be a motherboard, memory, power supply, thermal, OS, nor overclocking issue, they moved on to making Intel aware of the problem. They brought it to the attention of the MersenneForum people where the author of the code and several other community members worked to narrow down what was happening. To summarize the thread: When running an older version of Prime95 (which used the AVX codepath for all CPUs that could support it), some German overclockers were getting errors on one size of FFT-768K. It was later posted to the Intel forums once it was determined that it was likely a chip issue. The firm recommends that users contact system manufacturers or motherboard makers for updates. Intel has identified and released a fix and is working with external business partners to get the fix deployed through BIOS. In those cases, the processor may hang or cause unpredictable system behavior. This issue only occurs under certain complex workload conditions, like those that may be encountered when running applications like Prime95. Intel has identified an issue that potentially affects the 6th Gen Intel® Core™ family of products. Intel was quick to track down and identify the issue, and says it's working with motherboard vendors to issue BIOS updates as a workaround: Over- or underclocking the CPU doesn't have any effect on whether the bug occurs. Prime95 uses the fast Fourier transform to multiply very large numbers, and at least one particular exponent-14,942,209-causes Skylake CPUs to choke. The bug manifests when a certain calculation is performed. The folks at the Great Internet Mersenne Prime Search (who make Prime95) have come across a bug in Intel Skylake CPUs that causes affected systems to freeze. 'Tis a peaceful night after Christmas, and the ghosts of FDIV and TSX have come once again to haunt Intel.
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