CPU/Mobo Multi-meter vs. Motherboard: A Study of Voltage Readings

[undertaker]

A very informative article:
http://www.neoseeker.com/Articles/Hardware/Reports/motherboardvoltages/
Basically shows that if ur system is stable,there is not much to worry about for the mobo's sensor showing +/- 3% deviation from the ideal voltage.

To conclude, we can see that the claims of motherboard voltage sensor inaccuracy are well-founded to a degree. Whether or not some of the variances are anything to bog down your mind with is up to you to decide. Personally, I wouldn't be too concerned if my voltages were 2% off, but as the results showed, some of these variances can make quite the difference. In fact, I wouldn't hesitate to bet that some people have been scared into buying a new power supply just because of some low voltage readings that were the fault of the motherboard rather than the original power supply.

 

[Eazy]

With my ASUS P4C800ED board and Antec True 480 PSU I get the following readings....

By MotherBoard Monitor as well as ASUS Probe...

11.91
4.99
3.25

With a nice German Digital MultiMeter

12.04
5.06
3.28

I trust the DMM readings

 

[TheMask]

guys how are u measuring the voltages using the DMM? i mean on what connectors are u measuing these voltages?

On my A8N-E with Antec TP480, I measured on the Molex connector for +12V n +5V.

Asus Probe:

+12V - 11.648~11.712V

+5V - 4.892~4.919V

some local DMM:

+12V - 10.65V (steady)

+5V - 4.5V (steady)

 

[undertaker]

Masky,man ur 12v line is really low.The 450W colorsit I just got shows these using pc probe:
12v-12.6v/12.8v(idle/load)
5v-4.95/4.87
3.3v-3.3/3.28
Heavent measured with dmm yet.
I just got this smps to replace an older 400w one from the same company(claimed 400w coz the rails added up to a measly 237w).
This one is much better :
5v:30A,12:19A,3.3V:18A.Thats 437W total not bad for a Rs.1100 psu with dual fan with speed control as well.
For AXP users a lil lower 5v and a lil higher 12v is to be expected for certain reasons.For A64/P4 users however there is no such issue.

 

[TheMask]

well.. i am sure the voltage cant be as low as the ones given by my DMM. at those voltages the system wont be stable at all.. but i dont have stability problems.. system runs just fine, even OCed to 2.75gigz i cud run 3D Mark 03 n all

 

[undertaker]

I think there is some mistake in ur measurement or may be ur cheapo local multimeter is bad coz antec usually gives 1% deviation at most.In fact PSU may be rated according this criteria:
Percent deviation from ideal voltage(esp. if it s -ve deviation):
1%-excellent
3%-good
5%-average(most good local smps will meet this criteria)
Recent Intel spec sheets call for 3% regulation.

 

[Eazy]

guys how are u measuring the voltages using the DMM? i mean on what connectors are u measuing these voltages?

12v and 5v off the Molex and 3.3 from Aux Connector...

here is a chart of voltages and wire colours.....

 

[TheMask]

tnx for the pic bro.. but i am kinda concerned about the readings on my DMM now..

 

[Eazy]

tnx for the pic bro.. but i am kinda concerned about the readings on my DMM now..

You should not have a problem getting the DMM to read correctly - there normally is a POT (right word ?) inside which you turn to change the reading. If you compare your DMM against another one which has what you think is a more accurate readings then you should be fine. I have a friend who has an expensive DMM - a Fluke - and I matched mine to that meter.

 

[TheMask]

well.. mine looks conked (perhaps needs an internal battery change).. mine's a cheapo model n it reads 206V on the AC socket.. lemme see if i cud borrow another from a friend n check..

For once I am counting on Asus Probe than on my stupid DMM

 

[SunnyBoi]

for me,

Athlon 2500+ @ 3200+, 1.7V Vcore. Powersafe 500W

DMM :

Idle :

3.40V

5.10V

12.48V

Load ;

3.36V

5.05V

12.55V

ASUS Probe :

on my old board, A7N8X Dlx idle showed up as 3.26V, 4.95V, 12.41V. Load , same.

new board A7N8X E Dlx, Idle : 3.34, 5.026, 12.48V load : 3.36V, 4.999V, 12.552V

heh..talk about accuracy on the new board!!!!!!!

i was really worried abt the voltages at first when i got it, a quick reading thru the DMM proved me wrong

 

[Fakepunk]

I'm a little worried too.
Asus probes shows me 11.71 on the 12v line.I use a Smartpower 400w.
I don't have a DMM so I don't really know what the real story is.
I think that a 6800GT is not suitable for this PS, Won't you agree?
Anyhow its a temporary arrangment, hopefully my 6600GT won't be starved for any power.

 

[Aces170]

I have a cheap VIP 300 watts shows 11.712 on the 12V and it fluctuates a lot. Just had an issue once but that was with Cool n quiet enabled. Also I have a 9800 pro which is one power hungry card.

I wouldnt worry too much on the readings as my friend is using an AXP + 2 HDDs + 1 optical drive + 3 Fans + 2 Lan + 9800 pro on a 200 Watts generic Mercury powersupply @ 24hrs on and he hasnt had a single issue since more then a year now.

 

[Rockyme2002]

Yea same here Aces..........no problemo on a Generic PSU till now with loads of things attached. *Touches wood*
I had posted it smewhr....lemme get it

EDIT:
Here's the linky

http://www.techenclave.com/forums/showthread.php?t=2307

 

[Crazy_Eddy]

If you compare your DMM against another one which has what you think is a more accurate readings then you should be fine. I have a friend who has an expensive DMM - a Fluke - and I matched mine to that meter.

Are there any other methods to tune your DMM? I dont know anyone else around with a DMM

 

[undertaker]

Even my rig was running fine with Colorsit smps rated at just 5v:12a,12:10a,3.3v:13a.But When I saw the 450w one with sata,24 pin connector and dual fan w/ speed control for just 1100,I had to buy it.Atleast I don't have to worry when I add a new 6600/6800 later on.
BTW this company seems to be pretty decent:http://www.colors-it.com.cn

 

[Eazy]

BTW this company seems to be pretty decent:http://www.colors-it.com.cn

You imported your PSU from China ? If you did than the shipping must have been more than the cost of the PSU

 

[undertaker]

No man,got it staright from a warehouse in NP.LOL.

 

[bottle]

guys how are u measuring the voltages using the DMM? i mean on what connectors are u measuing these voltages?

On my A8N-E with Antec TP480, I measured on the Molex connector for +12V n +5V.
Asus Probe:
+12V - 11.648~11.712V
+5V - 4.892~4.919V

some local DMM:
+12V - 10.65V (steady)
+5V - 4.5V (steady)

i just got an el cheapo dmm today as well

tp 480 i got

+5v.......4.85v :O
+12v.....12.01v
neopower gave me

+5v......5.01v-5.03v
+12v....12.03v

was running prime when i was testing voltages if it makes any difference.. now anyone wanna tell me how to go about measuring 3.3v ?

 

[undertaker]

Use the main atx connector itself,there is enough space there for a dmm probe.Btw prime95 is nothing compared to cpuburn ,it literally tries to roast ur system alive. :rofl: