3 Replies Latest reply on Aug 25, 2016 7:25 AM by Intel Corporation

    Intel Microcode Update 36h Causing I7 5820K to Throttle to 900MHz on Boot for ~90 Seconds 9/10 Times

    ltron

      The CPU throttles to 900MHz (1200MHz is the official minimum) in most cases for approximately 90 seconds after I boot into Windows 10.  I have a Core I7 5820k and an Asus Sabertooth X99 motherboard and I have tried multiple BIOS versions with the same result.

       

      I first noticed this problem some time in November 2015 and this behaviour did not manifest itself when I got the computer in September.   When using Intel XTU it told me that it was throttling because it was hitting a current limit.  The current limit is 135A by default and according to Aida 64 I was getting nowhere near that.   The current going through the CPU was actually between 5 and 10 A so I have no idea why it thinks it is hitting this limit.

       

      I confirmed, however, that setting an arbitrarily large value for the current limit in the UEFI(I chose 450A)  was a workaround for the issue.  Aida 64 showed the current used to be around 15A at idle even after doing this, so nowhere near 135A let alone 450A!  I then installed Ubuntu Mate and found that it did not suffer from this problem unless I enabled the proprietary microcode in the additional drivers section, I tested this extensively to verify it.  This microcode was dated some time in November and this was when I started noticing problems.  So I concluded that this microcode is responsible.

       

      So, have I got a faulty CPU and this just happens to have been exposed by the new microcode or is it a bug and people haven't noticed as they are using XMP or some such, which tends to set the current limit at 1023A?  Any insights would be most welcome.

       

      My specifications:

      Intel Core I7 5820K

      Asus Sabertooth X99

      16GB(4x4GB) Corsair Vengeance LPX DDR4 3000MHz@2133MHz

      AMD Sapphire Tri-X 390X GPU

      Noctua NH-D15S Cpu Cooler

      Corsair RMi 1000W PSU

      Samsung 840Pro 256GB (Windows 10 64Bit)

      Crucial M4 256GB (Ubuntu Mate 16.04 64Bit)

      Samsung SM961 PCIe M2 SSD

      Phanteks Enthoo Evolv ATX Case