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how to calculate the power consumption of each component?

by Magic-wand / November 12, 2012 1:22 PM PST

If a power supply spec states that the maximum output is 240W, does it really mean it or 240W X 70%~80% efficiency?

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All Answers

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I'd need to see the PSU
by R. Proffitt Forum moderator / November 12, 2012 1:46 PM PST

The words matter here on the spec. I can't see the specs so I can't call it out. But it's worth knowing you want to tap the PSU at half or less it's rating if you want it to last and be trouble free. So a 240W PSU is good for 120W continuous duty.

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What could a 240W power supply do?
by Magic-wand / November 13, 2012 10:28 AM PST

That's why I want to know the exact power consumption of each component.

This is a HP 7800dc sff, CPU E8400, 4G DDR2 800Mhz(2 sticks).

I guess motherboard(Intel Q35 Express Chipset) consume about 40W or more, a harddisk and a DVD-RW each 20W, CPU 65W, and DDR2, USB...etc, that is well above the 120W limited, not mention to a PCI-X display card.

I wonder if the power supply could survive when any peripheral card added.

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Exact consumption
by pgc3 / November 13, 2012 10:39 PM PST

To be EXACT get out your schematic and break out your VTVM preferably a Fluke or similar standard, even then, there will be variables.

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exact power consumption of each component.
by bob b / November 14, 2012 8:06 AM PST

I'm sure that's possible but it might be beyond we mortals.

Most folks use this thing called 'tdp'........it refers to power.

For a normal system the 2 big power users are the cpu and the gpu.

Folks have their favorite method to determine the proper psu size.

Here's something that seems to work.
Cpu power + gpu power x 2 + 100w.

Best to get a single rail unit.......otherwise you might get into that load balancing non-sense.

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by bob b / November 14, 2012 7:27 AM PST

For a psu that refers to how well the unit can convert input power to output power.

300w input @ 80% efficiency equals 240w output.

A psu is rated with output power.........often it's wishful thinking.

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PS. Read this article.
by R. Proffitt Forum moderator / November 14, 2012 7:34 AM PST

Let me paraphrase the results.

1. Never run a 240 Watt PSU at 240 Watts or even at 70% of that.
2. Whatever you calculate, you're probably wrong. Aim high.
3. When PSU's fail, they can wipe out the entire PC.

There's a lesson here. No need to repeat it first hand.


PS. Old engineering saying follows.
"An engineer's experience can be measured by how many things they fried."
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A memory stick would consume 15W????
by Magic-wand / November 27, 2012 10:46 AM PST
In reply to: PS. Read this article.
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Then why use that at all?
by R. Proffitt Forum moderator / November 27, 2012 11:15 PM PST

This area is well traveled and the lessons are there for us to use again and again. Only those that want to repeat the lessons ignore the past.

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