Motherboard shopping

[markw at mohawksoft.com]

> markw at mohawksoft.com wrote:
>> 1st, with a good volt meter, while the machine is running, make sure all
>> the voltages are good. Sometimes people add cards and hard disks to
>> systems and overload the power supply and push the voltage down to where
>> the system sort of runs.
>
> This is a good idea, though with an intermittent problem it probably
> wont rule anything in or out as the cause. Making sure all the supply
> voltages are within 10%, or preferably 5%, of their ratings is a good
> check, but beyond that unless you know what your motherboard happens to
> tolerate it may not mean much.

Hell no!! +- 1% MAX!!! Any more than that will cause problems.

>
> Similarly, you can buy power supply testers fairly cheaply these days
> that will check the voltages under load, but without a load specifically
> sized to test your supply (or matching the requirements of your
> motherboard and peripherals), it'll only tell you whether the supply is
> generally functioning OK.

No the voltage regulation of an ATX power supply is not like a 9V
transformer, there are high precision high power devices. The 3.5V has to
be 3.5v. The 5V HAS to be 5V. The +-12 can be off a bit.

>
> You might want to try selectively adding and removing various high
> current peripherals (drives, video card) and see what the voltages are
> after powering up and letting things stabilize. If there's more than 5%
> change in any of the voltages, you're probably hitting the limits of the
> power supply.

Again, +- 1%

>
> If this is a home built system, it also might be a good idea to compare
> the rated wattage of your supply's 12 volt output (not the wattage of
> the entire supply) to the wattage requirements of your CPU. Many older
> supplies have high wattage ratings, but inadequate current on the 12
> volt line to run the latest CPUs. (Motherboards have on-board regulators
> that draw on the 12 V line to generate the CPU supply voltage.)
>
>
>> ...take out half the RAM. See if it still a
>> problem. If it is not, replace the first half of the RAM with the half
>> that was removed and see if the problem returns. If it does, one of
>> those
>> two ram sims/dims are the problem.
>
> This is also a good tip, and particularly handy if you don't have
> another system you can borrow some known working RAM from. I've used
> this technique on a number of occasions.