Which vcore reading to trust?

[FramePointer]

My CPUs vcore in the bios is set to offset mode (-0.010v). The bios shows the vcore fluctuating between 1.288v and 1.296v. When I am in windows, CPU-Z and AXTU (Asrock OC utility) show the max voltage never exceeding 1.264v under full load.

The CPU (2600k) is running at 4.5 Ghz stable and temps are all good, but which of these readings are to be trusted? I guess in either case it should be a safe vcore, but I would like to bring my voltages down as low as possible.

 

[Paragon]

They are both correct. Voltage in BIOS will be different than voltage in Windows. The CPU is loaded differently in each. Also, make sure that you are not reading VID voltage. This is more of a set point and not an actual voltage that increases as clock speed increases. VID at 4.5 should actually be around 1.386. With vdroop, your voltage will never reach the actual voltage setpoint.

 

[FramePointer]

They are both correct. Voltage in BIOS will be different than voltage in Windows. The CPU is loaded differently in each. Also, make sure that you are not reading VID voltage. This is more of a set point and not an actual voltage that increases as clock speed increases. VID at 4.5 should actually be around 1.386. With vdroop, your voltage will never reach the actual voltage setpoint.

My VID is actually about 1.396. I'm now running with a voltage offset of -0.020v. The bios shows a max of 1.284v and in windows I peak around 1.256-1.264. I'm curious about how the CPUs are "loaded differently". I guess that doesn't make a ton of sense to me. Under maximum utilization, is my peak core voltage 1.264 or is it 1.284? How can it be both?

 

[Forceman]

In the BIOS many of the power saving features are not activated, for one thing. So that can affect the voltage. Also , the CPU is running at full speed, but it may not be under enough load to actually cause significant Vdroop, but while loaded during testing it would be - so your Windows voltage would be drooping below the BIOS voltage.

 

[CPL0]

I'm curious about how the CPUs are "loaded differently"

While in BIOS setup your CPU will usually not run turbo multi's so for your 2600k that means the CPU will be running at most 3.4GHz with 100MHz BCLK. After post, depending on your LLC, usually your highest vcore will be when 1 thread keeps the CPU busy with a low load at the highest multi. A high load, depending on LLC, will usually give a lower vcore at the highest multi than a low load but at the same time with SNB VID can increase for higher loads at the same multi.

When using offset mode and a loaded CPU your vcore will be dependent on VID, offset, LLC and CPU current draw.