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Vcore drop

G

Grinja

Member
Hi,
I was CPU Z (I know software no good for measuring but just for) shows a Vcore of 1.392 (1.425 in BIOS). When I run Orthos CPU Z shows the voltage dropping to 1.368.

Should I be worried? 😕

 
Normal? Yes. Worried? No.

It's called Vdroop, and some boards have it worse than others. It can affect overclocking.
 
Yes. This is normal.

The voltage regulators for high-end CPUs are designed so that the voltage drops slightly under load, this allows the regulator to supply much cleaner power. A stricter regulator which doesn't droop under loader must overcompensate everytime the CPU changes load, causing much larger spikes and sags; the catch is that these spikes and sags are very short lived, so won't be caught by multimeters on on-board software monitoring, but they are just as damaging to the CPU).
 
Don't trust the software

CPU-Z reported my voltage fluctuating and whatnot, DMM proved that it wasn't at all. BIOS/other software reports my voltage at 1.325V and really it is about 1.38V.

Software voltage readings are not accurate.
 
Yeah..software is not too accurate. However, most boards show some droop when overclocked. The magnitude depends on how the Droop control is implemented in the Buck Regulator-PWM feedback loop. There should be a pin labelled "Droop" on your Buck-regulator datasheet. You might have to alter the RSense value if you want to minimize droop. The original setting is probably calibrated using a particular load-line...
 
I was really curious about this so I set up a test.
I just got a gigabyte p35-D3SL and started overlocking an E4500 on it.
To measure the voltages on vcore I used an oscilloscope connected to the fet output on the board.
I found something interesting.
The voltage in the bios , set to 1.38, was only 1.34 at the actual fet
When I ran the processor under load, both cores.
The voltage fluctuated between 1.3375 and 1.3425 .
The thing I found the most interesting is that after looking at the scope capture for an hour, it formed a perfect square wave output, with the 1.3425 being the peaks.

Not sure of why there is such a large diference in the bios setting of 1.38 and the actual output at 1.34. All other voltages, 12, 5, 3.3 stay well within spec.
 
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