confused about different cpu voltage readings

[suklee]

i5-2500k, on a Gigabyte Z68XP-UD3 motherboard.

In Vista I've got Core Temp, CPUID Hardware Monitor, Touch BIOS, and EasyTune6. The last 2 are Gigabyte programs. Can't use cpu-z because it doesn't read my Gigabyte mobo correctly (apparently).

Core Temp's VID shows idle at 0.99v (1.6GHz), but the rest show constant 1.34v. In fact, Core Temp's VID is constantly changing. When I run IBT, the CPU ramps up to 4.5GHz, Core Temp shows 1.4v+, but the other 3 show 1.28v. So Core Temp voltage goes up, while the other 3 go down. What's going on here, and which program is correct?

In BIOS, I've disabled Multi Steps Load Line, my Vcore is set at 1.350 and I didn't set any Dynamic Vcore (offset voltage). Should I change any of these?

Not sure if this means anything, when at default 3.3GHz, on "Auto" voltage BIOS sets it to 1.355v. When set at 4.5GHz, Auto = 1.385v.

 

[Idontcare]

Core temp is showing you what the CPU is asking the BIOS to supply it with.

At 4.5GHz, the CPU has been internally programmed to tell the BIOS to supply it with 1.4v+. (this is called VID, not Vcc...VID = CPU's requested Vcc)

Now asking is not the same as receiving, true in life for you as well as your CPU.

In your case you have instructed your BIOS to ignore your CPU's request for voltage and instead just give it 1.35V regardless what it thinks it wants. (this is called Vcc)

So your CPU is asking for 1.4v+ (VID) but your BIOS is telling the VRMs to give it only 1.35V (Vcc)

And because you disabled load line calibration (LLC) there is going to be some Vdroop going on as well when the CPU is loaded...hence that 1.35V supply droops to 1.28V.

1.28V is what your CPU is really receiving from the VRMs (but not quite, its a software measurement, so there can/will be error involved in this number as well).

 

[suklee]

Makes much more sense now, thank you. I wasn't grasping there was a difference between VID and Vcc, but now I understand it.

So now I have another question. With auto voltage on, my Vcc is auto-lowered to as low as 0.91v in Windows, or when I'm playing BF3 / running IBT, as high as 1.34v on 4.5GHz. Would this be better than giving it a constant voltage of 1.28v?

 

[Gillbot]

goes hand in hand with this: http://forums.anandtech.com/showthread.php?t=153761

 

[ehume]

Core temp is showing you what the CPU is asking the BIOS to supply it with.

At 4.5GHz, the CPU has been internally programmed to tell the BIOS to supply it with 1.4v+. (this is called VID, not Vcc...VID = CPU's requested Vcc)

Now asking is not the same as receiving, true in life for you as well as your CPU.

In your case you have instructed your BIOS to ignore your CPU's request for voltage and instead just give it 1.35V regardless what it thinks it wants. (this is called Vcc)

So your CPU is asking for 1.4v+ (VID) but your BIOS is telling the VRMs to give it only 1.35V (Vcc)

And because you disabled load line calibration (LLC) there is going to be some Vdroop going on as well when the CPU is loaded...hence that 1.35V supply droops to 1.28V.

1.28V is what your CPU is really receiving from the VRMs (but not quite, its a software measurement, so there can/will be error involved in this number as well).

I've bookmarked your post. A concise, fundamental explanation. Thank you.

 

[Idontcare]

I've bookmarked your post. A concise, fundamental explanation. Thank you.

As a HUGE fan of Hayao Miyazaki and all things Studio Ghibli, I take that as a big compliment thank you!

 

[suklee]

goes hand in hand with this: http://forums.anandtech.com/showthread.php?t=153761

read the above thread and think I now understand the multipliers / c-states / EIST etc...

Is there a way to specify a voltage at max GHz AND have it automatically throttle down with a lower voltage? (without using Auto?)