Voltage fluctuation question...

J

jmohnuofo

n00b
Joined
Jul 6, 2006
Messages
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Hey everybody, I am somewhat new to overclocking and have a question regarding my power supply and a voltage fluctuation. My setup is as follows:

AMD X2 3800+ - OC to 2.55GHZ
Thermaltake Big Typhoon 120mm
ASUS A8N-SLI
EVGA 7900GT KO Superclocked
1GB Kingston ValueRAM - buying some OCZ or G.skill soon
Thermaltake Silent PurePower TT-420AD(DUAL FAN) ATX 420W Power Supply 115/230 V UL, CSA, TUV, CE

Now my question is, the setting in my bios for my CPU voltage is at 1.425 and with it OC to 2.55GHZ, it runs stable after Prime95, SuperPi and 3DMark benchmarks. But when I look in CPU-Z, I notice my voltage fluctuating between 1.45 and 1.47v without any load (just sitting in windows). Why is it a little higher than what I set in the BIOS? Is this normal? Eventually I would like to get a new PS, but for now I will keep this one if it will work well enough. What do you guys think, is this a problem with my power supply?

On a side note, it seems that at about 2.6GHZ, it starts getting unstable (SuperPi starts giving me errors), but I can start stepping up the voltage to get it stable, how hight do you think is safe to go on an X2?

Again, I am new to this so any help would really be appreciated. Thanks!
 
Looks like I found some answers on the safest voltages for my x2 3800+. Most people say between 1.5 and 1.6 on air is ok, but to be safe stick around 1.5v. Still not sure why I have such a big difference between my bios voltage setting and my actual voltage.
 
I'm running an XP-M 2500+ at 250x9.5 and its set at 1.9v in bios. But moves from 1.82 - 1.87. If its stable don't worry. Voltages fluctuate, thats what they do. As long as your system runs stable voltage fluctuations are expected. Nothing to freak out about.
 
So when I want to set the voltage to, for example, 1.5v, I would monitor that by using CPU-Z, not by what I set in the BIOS, correct?
 
WARDOZER9 said:
Yup. That gives you a real time reading.
Click to expand...
However software readings are notoriously innaccurate. Software might say that voltage is fluctuating, but if you were to measure it with a DMM you would probably find it to be rock solid stable (with a good PSU).
 
BIOS/Windows voltage readings should be taken with a pinch of salt.
If measuring the same voltage lines with a multimeter you will notice less variation in the voltage.

Reading a voltage using a volt meter doesnt require any form of stability from the PC to get an accurate reading (its powered by a DC battery). Any variations in the PC's own power supply cannot affect the true readings.
Using a PC to monitor its own voltages goes through many more processes, there are more ways for variations to creep in. The quality of components used has to be brought into the equation as well as the use of a switch mode psu to power everything.
Also, inside a PC is a very noisy environment that is constantly changing as you use the pc. The monitoring circuits are built amongst the noise so that will impact the readings.

If you really need to know whats going on you must use a multimeter, preferably a good brand like Fluke, but most will do a better job than the motherboard readings.

If you do find that the real voltage is higher than you set in the bios, a few reasons spring to mind.
It is possible that the voltage regulator has been built with components that are out of tolerance thereby always giving you slightly more voltage than you set. You will have to just accept this unless you can adjust the software to compensate
The BIOS or monitoring software on your PC may be inaccurately written (for your sensor) and in need of an update.

Not quite the same example but I had an old motherboard that used to report a max temp difference of 6C when the temp had change 20C.
It would be nice if each motherboards sensors were calibrated and the compensations needed to give near accurate results saved and used in applications that need them.
This would at least give good ballpark figures but would still be prone to some fluctuations due to inherent noise in the PC.
 
Funny. MBM5 gives me damned near a perfect match with what I got when I checked with my multi meter.
 
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