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Old 12-29-2012, 04:13 AM   #1
cjae
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psu to motherboard mismatch


I bought a cheap 110v watt measuring tool, where you plug in a 110 source and a device into it and shazam, it tells you how many watts it is using. I bought a newer motherboard to replace what I assummed to be a power hungry penitum II, the kind from the ninties. The new motherboard is Motherboard : Integrated Atom D2700 : Mini-ITX : DDR3 : D2700DC : Intel.

I plugged the old tower running pfsense 2.0.1 into the watt meter and left sit for about fifteen minutes and it said about 20 watts. To check it I plugged in my light with a newer type coil light bulb. 13 watt and it said about 14-15.

So when I setup new board with same pfsense install to hdd this time a sata instead of pata, so this one might be a little faster rpm but the meter was only between 13-and 19 watts using the same psu from old box.

I know Im not using good test methods and I will check into hdds if needed the one box isnt here right now. The questions I am trying to ask are:

1. Isnt 20 for a old pII fairly low. Suspect
2. Does the matching of psu to motherboard make a huge difference

I might have even used the watt meter on the newer box before I did a hdd install meaning that the disk might not have even been spinning during reading (in the machine at all)

I thought the newer board would be considerably more efficient. The newer board seems to have a high cpu temp without a cpu fan 55 celcius.

3. Would this have a negative affect on the efficiency.

Last edited by cjae; 12-29-2012 at 04:15 AM.
 
Old 12-29-2012, 09:30 PM   #2
TobiSGD
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The Pentium II's thermal design power lies (dependent on the model) between 20 and 43W, which of course is much lower if the system is idling, so the measurements you take seem to be valid to me.
Of course the Atom CPU is much more power efficient, since it is much faster without having a higher TDP.
If you want to get even lower in power consumption you should use a highly efficient PSU (80+ Gold or better) with a very low wattage.
 
Old 12-30-2012, 03:33 AM   #3
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So just because a power supply is so many watts it does not mean that the system is constantly pulling that power. Ok, Well someone told me to get one of those smaller power supplies for use with small motherboards, or even ones used for embedded devices but I think those do not have the correct power pins interface. Would these power supplies make any kind of an efficiency difference? Or is it only the 80+% psus. Also I was thinkking of getting a fanless. Let me know what you think. Also thanks for reply.


So I looked around and saw this little psu, but it doesnt have 24 pin only 20. Does this atom only need a 20 pin input?

http://www.mini-box.com/picoPSU-80.

Would this be anymore efficient or is it just fanless and small form factor.

Last edited by cjae; 12-30-2012 at 03:57 AM.
 
Old 12-30-2012, 06:18 AM   #4
TobiSGD
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Quote:
Originally Posted by cjae View Post
So just because a power supply is so many watts it does not mean that the system is constantly pulling that power.
I am aware of that. It is about the 80+ standard: http://en.wikipedia.org/wiki/80_plus
 
Old 12-30-2012, 07:46 AM   #5
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The wattage and efficiency of a PSU are completely unrelated to each other. Any PSU plugged into any system will either provide the power needed by that system or it will fail because it cannot provide enough power.
If you want a fanless PSU, or a small formm-factor one, then buy one - it will not use any more or less power than a full-sized PSU with a fan provided it is of the same efficiency.
This is because the efficiency of a PSU is a measure of how much power it uses compared to how much it gives out - so a PSU which is 80% efficient will pull in 20 Watts when the system demands 16 Watts.
 
Old 12-30-2012, 11:39 AM   #6
TobiSGD
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Quote:
Originally Posted by 273 View Post
The wattage and efficiency of a PSU are completely unrelated to each other.
That is not completely true, you have to see that in conjunction with the actual power consumption. For example, on a system with 20W power consumption a 40W PSU that is compliant to the 80+ Platinum standard (89%/92%/90% efficiency at 20%/50%/100%) is more energy efficient than 80+ Platinum PSUs with 20W or 100W.
While I see your point that this usually is negligible it can make the difference when it comes down to the need of the absolute minimal power usage, size or heat production.
 
Old 12-30-2012, 11:52 AM   #7
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Quote:
Originally Posted by TobiSGD View Post
That is not completely true, you have to see that in conjunction with the actual power consumption. For example, on a system with 20W power consumption a 40W PSU that is compliant to the 80+ Platinum standard (89%/92%/90% efficiency at 20%/50%/100%) is more energy efficient than 80+ Platinum PSUs with 20W or 100W.
While I see your point that this usually is negligible it can make the difference when it comes down to the need of the absolute minimal power usage, size or heat production.
Good point, I was attempting to simplify and seperate the terms but as you say it pays to check the figures for the Wattages you expect.
 
Old 12-30-2012, 02:08 PM   #8
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Ok thanks everyone, that seems to have cleared that up for me, the reason I did I bought all this new equipment for my router is that everyone told me that using an old computer was so power inefficient that it was silly to even run. I can see that is not so much the case, but the new system is still slightly more efficient and is much more quieter so...it wasn't all bad.

Thanks everyone for your input.
 
  


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