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Calculation of VID for Ivy Bridge?

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Calculation of VID for Ivy Bridge?

Postby sp00n » Wed Apr 24, 2013 10:26 am

Can you explain how the VID value in CoreTemp is being calculated for an Ivy Bridge processor?
Searching the forums, I've found one post that states that the "i3/5/7 series do not report VID anymore", but this way back in 2010 and things may have changed since then.

Since the value is actually displayed for Ivy Bridge, there may be two ways to get that information, which is a) it is read directly from the CPU's VID table and provided "as-is", and therefore represents the "true" VID the chip would request from the motherboard if no offset value was entered.
Or b) the CPU does not provide a way to access its internal VID table entries, and therefore the VID displayed is just a function of the motherboard's Vcore value (by some clever logic to account for offset, Vdrop and Vdroop).

I've done some tests with changing the offset values and noting down the VID values, but the results were a bit inconclusive (and I've lost the spreadsheet during a crash in such a session *grrrr*), so I'd really appreciate if you could help me out here.
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Re: Calculation of VID for Ivy Bridge?

Postby The Coolest » Wed Apr 24, 2013 10:38 am

VID was missing on the 45nm Core i series. It was back with sandybridge.
And the VID Core Temp shows is as you mentioned in section a.
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Re: Calculation of VID for Ivy Bridge?

Postby sp00n » Wed Apr 24, 2013 11:10 am

So it's a direct reading from the CPU itself. Ok, thank you.
You should probably update your FAQ though then, especially point 17) and 18), which is still targeted at the older processor families.
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Re: Calculation of VID for Ivy Bridge?

Postby sp00n » Fri Apr 26, 2013 4:13 pm

Ok, now I'm a bit confused. If the VID is read directly from the CPU itself, why does it change when altering the "Additional Turbo Offset Voltage" setting?
It roughly correlates 1:1 with that setting, so when e.g. selecting +0.051v, the VID jumps from 1.3411 to 1.3861, and when selecting +0.102v, it goes to 1.4412. Shouldn't it be independent from any setting in the BIOS, be it the normal offset value or the turbo offset?
(It doesn't change when only altering the regular offset value, so something seems fishy here.)
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Re: Calculation of VID for Ivy Bridge?

Postby gilroy » Mon Jul 01, 2013 12:10 pm

I am doing some performance diagnostics and need as little background activity as possible. I am accurately controlling CPU %useage in a stress test which is tough when other items take up some CPU useage.
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