Why E5-2697v4 can not exceed 2.8GHz, no matter how many cores are in full load?

[YChen130]

Now I use it as Linux PC, and this problem does confuse me for a while.

It's confirmed that its max turbo boost frequency follows the number of cores enabled in BIOS, but not the number of full load cores.

Therefore even I can read Linux reporting this CPU's max frequency is 3.6GHz, it works only when 1 or 2 cores are enabled in BIOS, just like the turbo boost ratio table mentioned in the official datasheet.

I've dumped some MSRs for turbo boost ratio control, but found nothing incorrect.

Also I asked motherboard vendor whether they can handle it, but their customer service only replied that this motherboard tends to install Windows but not Linux.

Is there any way to fix it like changing some BIOS settings, or modifying some related MSRs on Linux?

p.s. It only works normally on Linux-4.8 with the original BIOS, and failed on the newer Linux kernel & BIOS.

[idata]

Hello ytchen,

Thank you for contacting the Intel community. Your processor is fine.This processor frequency is 2.30 GHz; the processor can reach 2.8GHz if the system requires it other than that you will not see that frequency, you can check this processor specification here:http://ark.intel.com/products/91755/Intel-Xeon-Processor-E5-2697-v4-45M-Cache-2_30-GHz http://ark.intel.com/products/91755/Intel-Xeon-Processor-E5-2697-v4-45M-Cache-2_30-GHz You can check the following links to understand Intel® Turbo Boost Technology:https://www.intel.com/content/www/us/en/architecture-and-technology/turbo-boost/turbo-boost-technology.html https://www.intel.com/content/www/us/en/architecture-and-technology/turbo-boost/turbo-boost-technology.html https://www.intel.com/content/www/us/en/support/processors/000005641.html Frequently Asked Questions about Intel® Turbo Boost Technology Best regards, Ivan U.

[YChen130]

Hi Ivan,

Thank you for your info.

I understand that this processor is based on 2.3GHz and having following turbo boost bins: 5/5/5/5/5/5/5/5/5/5/6/7/8/9/10/11/13/13.

When the other 17 cores are @ 1.2GHz idle state, the only one core in 100% load should be able to reach 2.3 + 13 x 0.1 = 3.6(GHz), but not just 2.8GHz, right? 2.8GHz is the max turbo boost bin frequency when >=9 cores are in 100% load.

With older BIOS and Linux kernel, one full load core can reach 3.6GHz when the other 17 are idle.

But after updating BIOS or using later Linux kernel, this problem came out.

Now if I want a core to reach 3.6GHz, all I can do is to disable 14 or 15 cores in BIOS.

I hope there is a way to solve this problem like modifying some certain MSRs on Linux, since this case is really weird.

Best regards,

YT Chen 2017/8/15 1220(UTC+8)

[idata]

Have you tried posting this information at the Linux* support site, they will be able to provide you with better support related to certain MSRs on Linux, unfortunately our support related to Linux*is limited here, you should be able to ask here:

https://www.linux.org/ https://www.linux.org/ Regards, Ivan U.