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

U

undertaker

Skilled
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.
Click to expand...
 
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
 
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)
 
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.
 
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
 
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.
 
TheMask said:
guys how are u measuring the voltages using the DMM? i mean on what connectors are u measuing these voltages?
Click to expand...

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

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



 
TheMask said:
tnx for the pic bro.. but i am kinda concerned about the readings on my DMM now..
Click to expand...

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.
 
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.. :D

For once I am counting on Asus Probe than on my stupid DMM :D
 
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 :D
 
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.
 
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.
 
Eazy said:
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.
Click to expand...
Are there any other methods to tune your DMM? I dont know anyone else around with a DMM :D
 
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
 
TheMask said:
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)
Click to expand...
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 ?
 
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:
 
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