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I am actually more curious about how a BIOS update could fix the bug.
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I was about to post something similar.
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There is a hardware design concept of 'chicken bits' - if as a hardware designer you have added a feature which you're pretty certain works, but are not absolutely confident you have tested perfectly, you add a not-publicly-documented bit in a control register that turns it off. The BIOS update would arrange to set that bit at boot time. It is entirely conceivable that this will reduce performance on some workloads - a typical chicken bit might be 'always pick the first two entries in the queue of instructions with their operands ready, rather than using a clever method to pick the most efficient pair'.
The Pentium FDIV bug was due to a wrong entry in a look-up table in ROM; in 1993 it would have been absurd to have 8192 chicken bits so that every entry in the look-up table can be corrected, and so there had to be a recall.
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The problem is apparently in the "HyperThreading plus the AVX1 pre-FMA3 code-path of the benchmark"; so if your CPU doesn't have HT you should be fine (the i5-6400, which is probably the most popular desktop Skylake CPU and what I have, doesn't have HT).