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

[idata]

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

[idata · Accepted solution]

Hello, ltron:

Have you provided this information to ASUS? Intel® Processors allow for minor software updates from within the motherboard BIOS specific to the processor; however, my recommendation in this case to resolve a microcode update error or a possible bug would be to contact the system or motherboard manufacturer for the appropriate information. Once they have checked this information and if the issue persists we can continue from there. It is important that ASUS as the computer manufacturer of the BIOS can check this scenario in case they have some reports or possible workarounds.

Regards,

Amy.

[idata]

Thank you very much for the reply. I just checked Asus' website and there was a new BIOS 3301 released at the end of July that I wasn't aware of. This has fixed the problem as it updated the microcode to 38h. I am surprised that this issue has persisted for almost a year as the people most likely to run at stock settings and hence encounter this issue are those who are less versed with computers. I, however, am just glad that the problem is now fixed.

[idata]

/thread/105416 ltron, I am glad to hear that you were able to fix this.

If you need further assistance let us know.Regards,Amy.