Power supply

E machine / T3604
June 1, 2009 at 00:34:45
Specs: Vista, 2gig ram Intel Celeron D
My question is. i recently installed a new video card geforce 9500gt and 2x 1gig ram cards

i'm wondering if my power supply is putting out enough voltage to support them
im using Speed Fan to measure my power and its saying

+2.5v : 1.48v
Vcore: 1.24v
+3.3v: 3.29v
+5v: 5.07v
+12v 11.56v

I've been running the computer for the last few days fine so far. but im worried if i could be causing damage to my computer by running it like it is.


EDIT : i dont know if it'll make a difference but my surge protecter is connected to an extension cord that connects to a wall outlet in my room.

See More: Power supply

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June 1, 2009 at 01:44:40
No it won't make any damage on your hard ware so don't worry if your power supply is not enough the computer will simple won't run.

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June 1, 2009 at 02:24:58
think WATTS not VOLTS

check this out:

as more peripherals more "Watts" will be required to
keep the whole system running
* USB accessory draws about 5 Watts per unit.
* Typical DVD ROM drive draws about 25 Watts per unit.
* Todays processors can draw up to 140Watts of power but
most idle lower than that.
* Modern graphics card (anything above a GeForce 6800) will
draw about 100 Watts
* The motherboard, CPU fan, Keyboard and mouse’ll draw
about 40Watts minimum.
* Hard drive’ll draw about 25 Watts each.
* Your standard 19" CRT monitor will use about 100Watts. An
LCD of the same size uses about 1/3 of that! That’s 33Watts.
Check the specs of your PSU
Does your PSU give you at least 60% of that???
best of luck

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June 1, 2009 at 05:37:41
I don't know what the +2.5v is? The other voltages are within the acceptable 5% +/- tolerance. Is it a Bestec unit?

"think WATTS not VOLTS"

Actually, you should think AMPS, especially on the +12v rail. It's nice to know how many watts a device requires, but where does that wattage come from? +3.3v, +5v, +12v or a combination of the 3?

If you remember the formula: watts = volts x amps

The voltages are fixed, so the amperage will determine the wattage. Some manufacturer's falsely inflate the overall wattage rating of their units by loading up the amperage on the lightly used +5v rail. It's not uncommon to see el-cheapo units with up to 50A on the +5v...decent quality units hold it to about 20A or so. The difference of 30A accounts for 150W (+5v x 30A) but that wattage is basically useless.

Never buy a PSU based on wattage alone. You should ALWAYS look at the amperage specs.

"Todays processors can draw up to 140Watts of power but
most idle lower than that"

True. And 100% of that power comes from the +12v. Do the math: 140W / 12v = 11.67A. Other devices that draw heavily from the +12v are the video card, HDDs, CD/DVD drives, cooling fans. If a PSU has more than one +12v rail, one is reserved solely for the CPU, the other(s) is shared by the rest of the devices. Having adequate amperage on the +12v rail is critical.

Debunking Power Supply Myths

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June 1, 2009 at 09:08:08
Thank you very much for the useful information. i think ill go ahead and buy a new power supply just to be on the safe side.

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June 2, 2009 at 07:20:51
Your voltage numbers say the supply is deficient. Either outputting insufficient current on 12 volts (and marginal on 3.3 volts) or just plain defective.

Demonstrated: a defective power supply is booting the computer.

Your useful replies say current (not wattage) is important. And that low voltage does not harm electronics.

Even the watts number (provided by one) for disk drives is wrong. In your case, the 5 volts has more than enough power, but the other voltages have insufficient power. Using published power numbers would have never seen this obvious defect. Watts report nothing useful AND are manipulated. A 350 watt supply from one supplier is also called a 500 watt supply by another (and neither has lied).

That meter has reported a failure before that failure caused a computer crash. Computer assemblers would have declared that supply as OK only because it booted the computer and due to insufficient electrical knowledge. Use the multimeter to confirm a new supply is also sufficient.

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June 2, 2009 at 14:35:48
"Your voltage numbers say the supply is deficient"

How so?? Granted, I have no idea what the +2.5v is supposed to be, but the +3.3v, +5v & +12v rails are all within acceptable tolerance limits. Here are the ranges according to Intel, Vex's voltages are in [brackets]:

+3.3v = 3.135v - 3.465v [3.29v]

+5v = 4.75v - 5.25v [5.07v]

+12v = 11.4v - 12.6v [11.56v]

You can download the ATX12V Power Supply Design Guide version 2.2 here:


"Your useful replies say current (not wattage) is important. And that low voltage does not harm electronics"

No one said wattage is not important. The voltages are fixed, the current is the variable. If you have the proper amount of current, the wattage will take care of itself. NEVER buy a PSU based on wattage alone, ALWAYS look at the amperage specs. But you have to know what to look for.

Power Supply Myths Exposed!

Where did anyone state that "low voltage does not harm electronics"?? Besides, as shown above, the voltage rails are not "low", they're within tolerance.

I think you need to read this article because all you're doing is perpetuating the myths:

Debunking Power Supply Myths

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June 2, 2009 at 16:19:17
While we're at it,

"A 350 watt supply from one supplier is also called a 500 watt supply by another (and neither has lied)."

Maybe neither has lied but one of 'em sure uses some "creative math" to arrive at 500w.

"Use the multimeter to confirm a new supply is also sufficient."

A multimeter wont confirm anything other than voltage is or is not present; same as the little power supply testers everyone sells. A real psu tester applies a load to each rail, measures the output, quality of the output, amount of electrical noise, and so forth. Even the timing of the power good signal can determine if a pc will boot or not. That's the equipment labs use to determine cheapo 500w psu's, for example, aren't capable of generating a combined 300w that can be used by anything. Those testers command 4 and 5 figure prices.

And, like jam said in Response Number 3

"If you remember the formula: watts = volts x amps"

A USB port uses a max 500ma of +5vdc power = 2.5 watts, not 5 watts. That's why USB hubs have only 4 ports at 100ma each when all are in use; the other 100ma is used to power the hub.

Modern hdd's use a pretty constant 12-15w and optical drives use between 10-25 watts depending if it's just sittin' there or reading/writing a disk.

Power supplies are probably the most important part of any machine; sure as hell the most misunderstood.

My rule of thumb is to allocate $100-150 for a quality psu then go shopping for a sale price and/or rebate to try and save a few bucks. I'll happily spend as much or more for a psu than a processor & motherboard costs.

It's probably true that most power supplies die a quiet death. But, the 1 or 2 out of 10 that die catastropically usually take a motherboard, processor, memory, or hdd chock full of data with them. I learned years ago to stack the deck in my favor and completely avoid cheapo overrated psu's...simply refuse to pull the trigger on a thousand dollar pc and power it with a 10¢ psu.

Read the links jam provided a few times and refer to them when you need to. It's sometimes dry reading but it's the info you need to know.


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June 2, 2009 at 22:22:25
> You can download the ATX12V Power Supply Design Guide version 2.2 here:

A 350 watt supply rated by one supplier is also rated as 500 watts by another. And nobody lied. They simply measured different things. Why those two numbers rate the same supply is obvious with necessary electrical knowledge, basic design experience (guess who has that), or an analysis using other spec numbers.

OP’s 12 volts is defective. Whereas these numbers are not identical to those in ATX12V specs, both numbers say same thing. Multimeter numbers are based in how voltages are measured, what is actually being measured, and how a multimeter works. When under maximum load, those power supply voltages must exceed 3.23, 4.87, and 11.7 volts. And yes, a multimeter can report numerous things from those simple measurements; when one learns how power supplies work or even designs them.

Review numbers provided by the OP. Another potential problem exists; seen only because he posted those numbers.. Apparently the computer has too much load on the 3.3 volts for that supply as compared to the 5 volts. Remember that myth about wattage? The meter shows why wattage says almost nothing useful. That supply could have more than enough watts. And most of those watts are lost on the 5 volt rail. Only current for each voltage is relevant. It appears that supply has more than enough power (watts) on 5 volts, barely enough on 3.3 volts, and is woefully undersized on 12 volts. Supply could have more than enough watts – just too many located on wrong voltages.

Another fact - if a power supply damages a motherboard or other components, the power supply was defective by design. Damage directly traceable to the human who bought or installed that supply. Since so many computer 'experts' have zero electrical knowledge, then an extremely profitable market exists dumping inferior supplies. Supplies that even violate industry standards such as UL and FCC. These same supplies will *forget* circuits that make motherboard damage impossible. Why can they dump these supplies in North America? Who are they selling to? A+ Certified computer techs who need not even know how electricity works to be certified.

A minimally acceptable supply starts at $60 retail. That does not say a $90 supply is better. But that does say a $30 supply is probably selling for an even higher profit margin by *forgetting* essential functions - such as the circuit that makes motherboard damage impossible.

Again, jam's numbers are correct. But then add other facts such as how a multimeter works and the various failure modes to convert those spec numbers into valid readings. By not learning this, jam would never understand why different multimeter numbers and spec numbers say the same thing. When under maximum load (that means the OS multitasking to every peripheral simultaneously and not disconnecting any wires), then those multimeter numbers must exceed 3.23, 4.87, and 11.7 on any one of each orange, red, purple, and yellow colored wire. Yes, three voltages - four wires.

"Volts times amps" assumes a perfectly resistive load. Computers are reactive loads. Total power required may not be the same power consumed. And so the difference between two numbers - watts and volt-amps. Add that to the specmanship game where a 350 watt supply can also be rated as 500 watts - when marketed to computer assemblers.

However, for a computer, all that is made easily irrelevant, instead, by viewing current for each supply voltage. Then by confirming those numbers are sufficient using a multimeter when the supply is under maximum system load - when the supply is powering everything in the computer simultaneously.

A defective power supply will still boot a computer. The OP's 12 volts was defective - and the computer still booted. Of course. Only way for a layman to identify a defective supply long before the system crashes is to use a multimeter. Only way for the OP to obtain useful replies from the more technically knowledgeable posters: numbers from that multimeter.

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