Re: A8N-SLI low voltage readings

In article <SWfKe.56466$Z52.355106@xxxxxxxxxxxxxxxxxxxx>, "Natéag"
<gaetanfo@xxxxxxxxxxxx> wrote:

> Here are my voltage readings with an Antec Neopower 480.
>
> +3,3Volts reads as 3,25
> +5 Volts reads as 4,84
> +12 Volts reads as 11,78
>
> On my previous boards all readings were
> slightly above nominal.
>
> I know that the CPU is not defective.
> I bought a new one, and results are
> the same !
>
> Is it current on that a sensor, chipset, BIOS problem on that
> motherboard (version 1.01), BIOS 1011 ?.
>
> If not the voltage regulator on the board may be
> defective.
>
> TIA.

First of all, don't panic.

None of your measurements are critically low. It looks like your
hardware monitor chip could be erring on the low side. To
determine if that is the case, you'll need to buy or borrow
a multimeter. I've found my ATX PSUs to be much closer to the
correct value, when they are measured by my $100 multimeter,
than when they are measured by the hardware monitor on
the motherboard.

The CPU plays no part in the measurement error, so replacing
the CPU won't do anything. Only if the CPU was completely dead,
and you couldn't get any video output, would changing the
CPU make a difference.

The measurement error on the motherboard consists of two parts.
The hardware monitor chip has an internal voltage reference
used by the ADC. That will have 1% or more error. If Asus is
using 1% resistors for the two resistors in the voltage
divider on each monitored input, those errors add, so the
total error could be 3%. There is no factory calibration
involved here, no potentiometer adjustment to set the gain,
so those errors cannot be dialled out (although it would not
take much work to make that possible, I don't think any
motherboard manufacturer really cares about this issue).

So, if you are still curious, buy or borrow a multimeter, and
see what it reads for each voltage. You can gain access to
+5V and +12V, by using a disk drive cable, and connecting the
multimeter there. Set the multimeter to "DC volts", being
careful to plug the two leads into the holes used for volts
and ohms (not the ammeter holes, as that would result in you
shorting out the power supply, and you'll blow the internal
fuse in the multimeter).

Paul
.

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