Min Allowable Voltages?

[Major_A]

I built my nephew and niece a computer so my brother in law could get work done. Right now the computer isn't stable in a game environment. Surfing the net, playing flash games, etc... is stable. But once you put a load on the machine you'll get various crashes. At first I thought it was a driver issue and updated all the drivers, and cleaned all the leftovers. Today I noticed that the +3.3V and +12V are all out of whack.



System Specs:
AMD Opertron 170
3GB DDR
Foxconn nForce4 motherboard
Radeon HD3850
1xHDD+1xDVD
4x80MM Case Fans
Cooler Master eXtreme Power Plus 500W
USB Wireless N NIC

[hnzw_rui]

Assuming those voltage readings are accurate, there's nothing wrong with the +3.3V and +12V rails. Iirc, the ATX spec allows for ±5% tolerance.
+3.3V: +3.135 V to +3.465 V
+12V: +11.40 V to +12.60 V

[Major_A]

How much power does the HD 3850 pull on the 12V rail when it's loaded? Every game, no matter how novel (LEGO Star Wars, etc...) crashes just as fast as Batman Arkham Asylum. I'm at a loss if the power supply isn't the culprit.

[hnzw_rui]

HD 3850, 95W TDP, I think, which probably equates to 8A on 12V. Iirc, that Cooler Master PSU is only good for 400W but that build shouldn't be pushing anywhere close to 400W. Why not do the usual torture tests: MemTest, IntelBurnTest, Prime95, Furmark. If all tests except Furmark pass, then it's probably just the GPU with the problem.

[Major_A]

I guess I'll have to run some tests next time I'm over there. My niece is whiny enough without the computer constantly crashing/locking up on her. Truth be told it just might be the board. I was given this board brand new and have had to fight with it tooth and nail just to get it to boot. It could also be the Corsair RAM in the computer. It's a 2GB kit with a PQI 1GB kit. The Corsair is rated at 2.5-3-3-7. I have the computer running at 3-4-4-8 2T to match the timings of the 1GB kit. The first stick of Corsair RAM I owned was PC3200 when PC2700 just became JEDEC certified. The timings for that RAM were 2-2-2-6. If I adjusted any of those values, even loosed them then the RAM would have all kinds of errors. I've been meaning to pick up a multimeter. Here's my question for measuring with a multimeter. Can I just hook the multimeter leads into the 12V pins on a molex connector and that represent the "real" 12V value? Sorry I was a bit all over the place there, thanks for your help.

[skier]

well what do you want to measure? just the 12v+ PSU voltage? if so I believe it goes like this:
Any Black-Yellow: 12v+
Any Black-Red: 5v+
Any Black-Orange: 3.3v+

but i havnt tested it in a looong time so i am likely wrong, but you'll know because any of the values will be close to their normal (yellow and red won't both be at 5v lol)

i'll grab my multi and test another PSU in a bitin a bit to make sure which is which, gotta eat first tho, it's 7 and i havn't eaten since 11

[Major_A]

I guess my main question there was is the 12V supplied to the molex the same 12V being supplied through the 24 ATX plug? Sounds like a stupid question but I don't know. I know that yellow and black are 12V and red and black are 5V (I always adjust molex case fans to 7V or 5V if they are too loud at 12V). I have no idea how to measure the 3.3V if I had to. If it's orange then that would mean tapping into the 24 pin plug, right?

[skier]

I guess my main question there was is the 12V supplied to the molex the same 12V being supplied through the 24 ATX plug? Sounds like a stupid question but I don't know. I know that yellow and black are 12V and red and black are 5V (I always adjust molex case fans to 7V or 5V if they are too loud at 12V). I have no idea how to measure the 3.3V if I had to. If it's orange then that would mean tapping into the 24 pin plug, right?

yes, i mean you can just stick the multimeter into the pins of the 24-pin if you wanted, but on the molex is the same i believe (and easier to get to), at least I know it is for my single rail PSU, it *may* be different with multi rail units, but i don't think so

[westom]

Assuming those voltage readings are accurate, there's nothing wrong with the +3.3V and +12V rails. Iirc, the ATX spec allows for ±5% tolerance.

Please learn how meters measure. Those 3.3 volts and 12 v numbers (if accurate) mean both voltages are defective. But those voltages are measured by a monitor. A motherboard voltmeter that is not yet calibrated. Calibration means using a 3.5 digit multimeter to measure any red, orange, yellow, and purple wires from power supply to motherboard. Measure by pushing the probe into the nylon Molex connector to touch the conductor. BTW, a voltage on the gray wire might also report something useful.

According to those numbers, 3.3 volts is marginal. 12 volts is completely defective. It may be due to a defective supply. Or a supply with insufficient current on those two voltages. An example of why supplies are selected based on current for each voltage; not on wattage.

Of course, no supply can be measured without a full load. Valid numbers possible only when a supply is connected to a computer.

[bubba]

Even though the voltage may be with in the 5%, dont mean the hardware likes the swing.

I have never trusted the voltages from any software. If the 12v rail is that low at idle then yes the PSU may be crapping out, or very weak. Voltage will drop as the system is loaded. So if you start low, it will only go lower.

Load the system and check the rails with a voltmeter. Its the only way to be sure.

[Major_A]

I still don't have a multimeter but here's a small update.
A) Loaded up Prime 95 and Furmark and the lowest I saw the 12V dip was to 11.71V.
B) I ran several 32M SuperPiMod runs and didn't get any errors. I didn't have access to a blank CD over at their house and I forgot to take my UBCD. This was the best RAM test I could come up with given what I had to work with.
C) Despite what nVidia's nForce download says I installed the latest package (15.49 I believe). Most of the crashing has stopped now. Maybe it was a gimpy northbridge driver?

I do plan on running the computer with a multimeter but that will have to wait. For the mean time my niece seems happy that she came play LEGO Star Wars.

[bubba]

I know how she feels, I loves me some Lego StarWars LOL

11.7 under load is with in tolerance (not great, but in tolerance), 11.7 at the desktop is bad. Sounds like the driver was the issue.

[Major_A]

I borrowed a multimeter from my dad, so I'll see what it reads in the next few days and report back.

[Major_A]

Calibration means using a 3.5 digit multimeter to measure any red, orange, yellow, and purple wires from power supply to motherboard.

Ok looking up schematics of the ATX plug the purple wire is +5Vdc VSB standby Voltage, explain to me what this does exactly. I'm heading over there in a bit and plan on measuring every red, yellow and orange line on the ATX plug. I might even see what the readings are using the PCIe power plug going into the video card. Unfortunately this is a dual rail unit so even if one rail it good that doesn't mean the other is. And this only adds more time to test each connection.

[westom]

looking up schematics of the ATX plug the purple wire is +5Vdc VSB standby Voltage, explain to me what this does exactly. I'm heading over there in a bit and plan on measuring every red, yellow and orange line on the ATX plug.

Do not measure *every* wire. Again, the sentence said what to measure. "Calibration means using a 3.5 digit multimeter to measure *any* red, orange, yellow, and purple wires from power supply to motherboard." It should take less than a minute. And should report in that minute what others do not discover even after one hour of swapping parts.

Measure these voltages to calibrate a hardware monitor. Another misunderstanding. Software never measures voltages. Software only reads voltages measured by hardware. The distinction defines who actually knows hardware and who is just reciting hearsay. A multimeter is calibrating hardware on the motherboard. Software never measures voltages.

When you power a room light, its switch remains closed. But when you power a computer, the switch is only momentarily closed. Why does a computer remain powered on? Because another critical component of a power 'system' is its power controller. Power controller sees a power switch closed for only a second. Then goes through a long procedure to power up the system. Even the CPU waits for the power controller to tell it what to do. Those many electronic decisions require a dedicated power supply - the purple wire.

A purple wire powers the power controller (in computers, as well as TVs, cars, etc). Therefore never add, remove, or disconnect anything from a computer without first removing its power cord from the wall receptacle. Those other three voltages (orange, red, and yellow wires) power only when the power controller orders it. A power controller must have its own separate power supply - the purple wire.

And finally, another said 12 volts at 11.7 is OK. He is wrong because he only read the numbers. Did not apply those numbers to other facts to have an accurate conclusion. Numbers without first learning what they mean is how so many jump to erroneous conclusions.

Above was only to calibrate a hardware monitor. To determine good voltages, you must first create a major load. Despite popular myths, Prime95 does not create a sufficient load. A significant load exists when the system multitasks to every peripheral. For example, play complex video graphics (ie a movie), while downloading from the Internet, while playing a CD, while searching the hard drive, while powering devices via USB, while ... Now useful numbers are obtained from any orange, red, purple, and yellow wires. Numbers that means almost nothing to you. And numbers that say everything to the few who actually know this stuff. If a yellow wire measures 11.7 volts, then a serious problem exists. Those who only read a spec number (did not learn the significance of that number) would assume otherwise.

Defined above are two procedures. One to calibrate the hardware monitor. A second to discover a hardware failure (even though the computer boots and executes).

[bubba]

on any molex plug measure the red to black, and yellow to black. at both idle and load. For both readings for the 12V rail (yellow) should be above 12V, ATX specs say it can vary. The lower the reading the worse off it is. If it has multiple 12v rails the rails will be separated, yellow wire with a stripe of some color. Different color strip for each rail.

Orange 3v+
Red 5v+
yellow 12v+

measure between those and any black wire. check readings at idle and load.

If its under 12V at idle the PSU is week or bad. If it drops under 12V under load the same applies. Like what has been said before the 12V rail can vary and 11.7 is in the "allowable" range, doesnt mean the hardware likes it.-

[westom]

Like what has been said before the 12V rail can vary and 11.7 is in the "allowable" range, doesnt mean the hardware likes it.-

Again, an example of reading numbers while ignoring facts behind those numbers. A meter reading 11.7 means 12 volts is probably operating as low as 11.4 volts - or lower. With basic electrical training, one can say why. Too many only read the multimeter number. Do not understand what that number is really reporting. A reading of 11.7 suggests voltage at 11.4 when basic electrical concepts are included. As numeric specifications say, 11.4 is a failure.

Numbers do not lie. Numbers require a tech to also understand what is being measured and why. 11.7 reports a power system failure.

Also important is voltage on the purple wire.

[Major_A]

Well... I don't think it's power any more. I ran Memtest86+ for a few hours and it came back clean. I'm starting to think the motherboard is just bad. While surfing the internet the computer shut itself off, didn't restart, just shut off. I checked every log file on the machine and I still couldn't get a clear indication why everything was crashing.

[bubba]

its bad replace it.

sorry, misread chart.

[Major_A]

How do you know? Because the 12V slightly dips below 12V?

Thanks for the help guys, clearly I don't know my *** from a hole in the ground with this.

*Further Confusion Edit*
I brought the PC home with me. I noticed on the SATA connector there is a solid yellow and a yellow with a black stripe converging on the same plug (means it represents both 12V rails, correct?). I tapped into that and I just ran the SF4 benchmark again. This time the lowest the meter dipped was 11.99V, the other 98% of the time it was at or above 12V. However, in the middle of the benchmark the PC locked up enough where I had to press the reset button. I'm about to format this POS and install Windows 7 on it.