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JMuel3
Beginner
1,429 Views

AVX issues with i5-6600K Skylake

Hello,

I have been having some issues with AVX, BLAS, and matrix multiplication with my i5-6600K Skylake CPU. OS is Windows 10 with developer mode enabled and linux subsystem for windows installed. BIOS is up to date. I've tried the following:

  • OpenBLAS on linux subsystem for windows passes all self-tests with all AVX disabled.
  • OpenBLAS on linux subsystem for windows fails self-tests with AVX enabled and AVX2 disabled. OpenBLAS fails the self-tests in inconsistent ways. It will usually, but not always, fail matrix multiplication tests such as dgemm. When it fails dgemm, it will occasionally compute erroneously large matrix products (on the order of 1e+70 when the expected result is on order 1). The error occurs randomly in unpredictable locations.
  • OpenBLAS on linux subsystem for windows fails self-tests with AVX2 enabled in the same fashion.
  • When using Octave on windows with OpenBLAS, it will occasionally report erroneously large values when multiplying matrices. I believe this is from the same underlying problem as OpenBLAS on the linux subsystem. Again these mistakes occur at random but are obvious (product on the order of 1e+300 when it should be on order 1 ) and happen frequently enough to derail large matrix multiplications.
  • Octave on windows with reference BLAS works as expected.
  • I've installed numpy and scipy with anaconda (which uses MKL) and matrix multiplication with these codes fails in the same fashion as Octave with OpenBLAS.

Given that BLAS is making random mistakes in both OpenBLAS and MKL, I'm guessing the problem is with the processor. I tried:

  • Prime95, which consistently fails on one core.
  • Intel Processor Diagnostic Tool passes.

Any ideas on what could be wrong or things to try next?

Thanks!

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8 Replies
idata
Community Manager
166 Views

JonMM: Thank you very much for joining the Intel® Processors communities. We are sorry to hear the processor is not working as expected.

 

 

In order to provide the most accurate response for this scenario, we will start a research on this subject, as soon as I get any updates I will post all the details on this thread.

 

 

Any further questions, please let me know.

 

 

Regards,

 

Alberto R

 

JMuel3
Beginner
166 Views

Hi Alberto,

Thanks for looking into this issue! Do you have any updates?

Thanks again,

Jon

JMuel3
Beginner
166 Views

Hi Alberto,

Thanks again for looking into this issue. It's been a week - do you have any updates?

Thanks,

Jon

JMuel3
Beginner
166 Views

Hi Alberto,

Any updates on this issue?

How long should I wait for a response before we try an RMA?

Thanks,

 

Jon
JMuel3
Beginner
166 Views

Update: I did a clean install of Windows 10 without the linux subsystem, and it still fails matrix multiplication tests in Octave with OpenBLAS.

idata
Community Manager
166 Views

JonMM: Thank you very much for letting us know that information. We apologize for all the lateness and for any inconvenience.

 

 

I just received an update on this matter and actually the problem could be related to the processor itself. To confirm if that is the case, please get in contact directly with Intel in order to replace the unit or if you have the option to test the system with a different processor you can always try that as well:

 

 

Chat support:

 

http://intelsupportchat.force.com/icslivechat/ics_tech_processor_ww_english_Chat http://intelsupportchat.force.com/icslivechat/ics_tech_processor_ww_english_Chat,

 

 

For phone support, depending on your location, you will see the contact information on the links below:

 

EMEA contact information: http://intel.ly/28QeAF3 http://intel.ly/28QeAF3

 

APAC contact information: http://intel.ly/1ITfjUF http://intel.ly/1ITfjUF

 

LAR contact information: http://intel.ly/29c0rW4 http://intel.ly/29c0rW4

 

North America: Phone Number 1-916-377-7000, Monday - Friday 7:00 AM to 5:00 PM (Pacific Time).

 

 

Any questions, please let me know.

 

 

Regards,

 

Alberto R
JMuel3
Beginner
166 Views

Final update: I returned the processor to Intel and the new processor they sent me works as expected. This problem is now solved; it was a defective processor.

idata
Community Manager
166 Views

JonMM: Perfect, thank you very much for letting us know that information. We are glad to hear the problem got fixed by replacing the processor.

 

 

Any other inquiry, do not hesitate in contact us again.

 

 

Regards,

 

Alberto R