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Skylake CPUs can freeze running Prime95

Soldato
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http://www.theregister.co.uk/2016/01/11/math_bug_splatters_skylake_intel_working_on_fix/

TheRegister said:
Intel has confirmed it's pushing out a BIOS fix for a bug that can freeze its Skylake processors.

The good news is that the bug's triggered by complex workloads. It was turned up by prime number experts the Great Internet Mersenne Prime Search (GIMPS), who use Intel machines to identify and test new large prime numbers.

A few weeks ago, this post popped up on an Intel community forum. The poster said the bug “can freeze any system that has a Skylake processor”.

Since the bug has been reproduced on Windows and Linux systems, and on different motherboards, that post posited that it had to be down to the Intel processor.

In the case of the GIMPS, the freeze was observed on the Prime95 application. Prime95 uses Fast Fourier Transforms to multiply extremely large numbers, and a particular exponent size (14,942,209) leads to the crash after “minutes or hours”.

Last Thursday, on the same forum, Intel confirmed the issue, posting that “Intel has identified and released a fix and is working with external business partners to get the fix deployed through BIOS.”

It told posters on the forum to get in touch with their OEMs for the fix.

Mersenne primes are prime numbers which obey the formula Mn = 2n - 1* (the first Mersenne prime is 3, and the largest currently known is 257,885,161-1).

GIMPS founder George Woltman wrote the Prime95 software, and Wikipedia notes the group has turned up all of the Mersenne primes confirmed since 1996. ®

* Where "n" is a prime number

Takes me back to the Pentium PRO days, we don't see many CPU bugs which have a real impact these days. Will the BIOS fix which I assume is a microcode update for the CPU limit performance in certain operations I wonder?
 
Isn't it a bit strange that this can be fixed via a BIOS update? I'm sure the last time there was such a fix it decreased performance because the only way to fix the bug was to disable a particular feature. Might've been an AMD issue, that one.

A lot of CPU instructions are implemented in microcode on modern CPUs. BIOS patching of microcode instructions has been around for a long time now.

Prime 95 no one needs!!!

Unless they're looking for prime numbers ;)
But there are other ways to stress test CPUs like you've said before.
 
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