Intel® Turbo Boost engages automatically and depends on the processor’s temperature, voltage, power, load, and the number of cores being used. We suggest making sure this feature is enabled in BIOS or contacting the motherboard/system manufacturer.
I have exactly the same issue like skraftnm. My system is the following:
Motherboard: Asus Maximus VI Hero; BIOS version 1603 (latest version)
Memory : HX321C11T2K2/16; Kingston HyperX 16GB DDR3 Kit
• JEDEC: DDR3-1600 CL11-11-11 @1.5V
• XMP Profile #1: DDR3-2133 CL11-12-12 @1.6V
• XMP Profile #2: DDR3-1600 CL9-9-9 @1.6V
Graphic Card: None. I use the one built in the CPU for now.
Monitor: HP LP1965
Storage #1: Samsung 850 Pro 256 GB SSD
Storage #2: Seagate 500GB 7200 HDD
CPU Cooler: CM Hyper 212 EVO
Case: CM HAF 922
Power Supply: CM Silent Pro M700
OS: Windows 7 Ultimate 64 bit
In BIOS I have turbo boost enabled, core ratio is on Auto. If I try to change manually the core ratio to anything higher then 38 in goes back to 38. Bus speed is 100 by default. I have got the feeling that max turbo frequency of this CPU is locked to 3.8 GHz Can someone from Intel confirms that this CPU is capable of reaching 4.0 Ghz or 3.8 is its maximum?
Please make sure all cores are enabled in BIOS. In Windows* System Configuration utility (msconfig) we suggest leaving the Boot Advanced Options as default, so Number of processors should be left unchecked.
You may also consider updating the BIOS.
Thanks for the reply joe_intel. After some trial and error I found that setting in BIOS - AI overclock tuner from XPM to Auto solved the problem. Now my multiplier is 8-40. and I can see some cores reaching 4.0 GHz. If I understood correctly from the CPU specification if 1 or 2 cores are actively working they can reach 4.0 GHz, with 3 working cores frequency is locked to 3.9 GHz and with all four working frequency is up to 3.8 GHz. Is that correct?
You are getting the idea behind it; nevertheless, such values may not be necessarily correct.
Page 45 of the datasheet provides more details: https://www-ssl.intel.com/content/www/us/en/processors/core/4th-gen-core-family-desktop-vol-1-datasheet.html