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Power supply 12v question.....

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Duvie

Elite Member
My recent woes in oc'ing my cpu and restarting it has made me wonder about the reason...

I had tried about every component except new ps...It is a new 350 sparkle PS but I noticed the 12v is at like 11.77v...Is this a sign of the rail dropping and could be a reason while during restarts I have a 50/50 chance of not rebooting properly instead getting a no monitor signal and monitor shutting off?

My old 250 which is at my moms as an extra I believe had 12v at like 12.03 or 12.05...actually all my voltages where a tad higher in their categories and now they are lower...What do you think??? same mobo and most all other components...

It is not the proc as it strted doing it with my 750 which had been fsb oc'd successfully for 3 months...I changed all the ram...removed any cards I had added...unplugged some devices to lessen the load...everything else had ran successfully at 112fsb for the 3 months...Now even a 102fsb will cause the restart problem...

System temps are better then 750 days...

No oc...absolutely NO problems...so I consider this just annoying but not an issue as oc should always be considered a bonus. However I enjoy the boost. If I never shutdown I am fine and don't get any errors. It is a pain when installing prog and needing a restart and wham no boot, then get registry errors when I hold reset for 4 seconds and it post.
 
Specs on computer PS voltages are plus and minus 10%. What is more important than the voltage level is whether or not it is spiking up and down or whether it has other noise impressed on the supply current. These are the types of problems that can affect the triggering levels of all the digital circuits in the machine. All it takes is one spike on one switching event out of hundreds of billions to produce a random crash. The big mystery is how computers manage to work at all.
 
Well I haven't noticed any spiking and I have had MBM program with votage tachs on and I have not seen anything. But at start up I can't see those voltages so I don't know. I tried unhooking some of the fans and drives and it didn't seem to help.

The Ps I got from a company that the first one they sent me was fine then started going haywire 2 days later with restart after restart and flashing led lights all over the place. I threw back in trusty 250 watt ps and no problem for the week until I got the new PS.

The sad thing is I don't even think the 250 is AMD approved, but the sparkle and first PS were...

Is there a northbridge chipset that is prone to this restart problem??? It didn't do it for the first 3 months but maybe it degraded over time...HMMM???
 
Duvie:

Ignore the message I initially sent you directly. Until I had read your "Power supply 12v question....." article I thought you were referring to a different set of issues.

Three thoughts come to mind:
(1) Have you tried running your computer with all cards but graphics card removed? Then try adding cards one-at-a-time until the problem seems to re-occur.
(2) Have you tried shorting the pins that cause your bios to revert to the default values?
(3) It would be very interesting to see how your system would perform with a mother board swap. Does anyone you know have the same motherboard and would they be willing to lend it?

Note: I believe that motherboards take one or more of the power supply voltages and step them down and regulate them to produce the specific voltages for each type of cpu. Remember, some motherboards let you adjust the voltage to your cpu.
While your power supply may be putting out the correct voltage, the step-down and/or regulation taking place on the motherboard may be whacko.

A final set of cautionary notes:
Taking voltage readings is a good idea. However, there at least three problems that a meter won't (or might not) detect. One is random high frequency noise riding a voltage. Second are swings in voltage. What you see on a meter on are voltage average. If for example your 12vdc was swinging rapidly up to 15v and down to 9v at a high rate, your meter would show a nice comfortable 12v. Yet this obviously would not be a desirable condition. Thirdly, you need to view voltages under several operating conditions. A marginal power supply might work just fine until, picking a device at random, your cdrom spins up. At which time the voltage might drop precipitously because an additional load has been applied.

Keep us posted.

I will keep an eye on the posts under your "Power supply 12v question....." article.

The sort of problems you are having are exasperating. You have my sympathy.

Good luck and best wishes!
 
You should look elsewhere than the 12V supply, my 300W PS only put out 10A @12V, I have 4 9.1GB SCSI HDs, 2 30GB IDE HDs, a SCSI CDRW, a 12x IDE DVD, and a SCSI zip drive, plus multiple fans.

All put a big load on 12V (11.43V by MBM) with zero problem,
 
Any ideas what to look at??? I am going to try old 250 ps this weekend with some devices unplugged as it doesn't have enough connectors, but I have tried that already with this 330ps and it didn't make diff. I am going to unplug dvd-rom and one fan and it should all connect. If it powers up and let me oc without restart error I guess I will have somewhat of an answer.


Could it be a problem with the northbridge?

How about my radeon? all other cards have been removed since and still no diff.
 
The old IBM PC specification for +12.0V is +5%, -4%, and I believe this is stricter than the current ATX specification. Since your 11.77V measurement is just 2% below the nominal value, don't worry.

 
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