[K12OSN] alternative power supply

[Rob Owens]

One thing to remember about power supplies is that the rating on them is actually the maximum rating.  The power supply doesn't automatically produce that much power--something has to draw that power from it.  Additionally, that maximum power rating is usually divided up among multiple power outlets which you plug into your hard drives, cdroms, etc.  

For simplicity's sake, lets assume that you have a 400W power supply with 10 power leads coming off of it.  Each power lead would be capable of providing 40W.  If you unplug 9 of the power leads (no hard drive, no cdrom, etc.) and only leave the motherboard plugged in, your power supply will now only produce a maximum of 40W, simply because there is nothing else to draw the power.

Generally, there are efficiencies to be gained by sizing power supplies close to the real power requirements.  So using a 400W power supply to produce only 40W will probably waste more electricity than using a 100W power supply to produce 40W.  I'm speaking in generalities here, and I don't know if this will make a big difference in the case of thin clients or not.

The best thing to do would be to actually measure the power consumption.  You could do it on the input side and you wouldn't have to open the case.  Or you could measure it on all the outputs, but then you wouldn't be accounting for wasted power in the form of heat produced by the power supply.  Measure it and see if you think it's excessive and if it's worth your time to try to reduce the power consumption.

-Rob


 --- On Thu 12/02, Gavin Chester < sales at ecosolutions.com.au > wrote:
From: Gavin Chester [mailto: sales at ecosolutions.com.au]
To: k12osn at redhat.com
Date: 02 Dec 2004 13:25:48 +0800
Subject: [K12OSN] alternative power supply

In a related thread we were discussing power saving on the client<br>monitor.  A supplementary question I have is related to getting rid of<br>the original client PC power supply:<br><br>You save some power by having a diskless (thin) client without the<br>overhead of running multiple disks.  However, you won't realise full<br>power saving if you leave in the 250-400W power supply and fans that<br>these PCs come with.  I don't know the levels of power consumed without<br>disks, but it will be much more than warranted.  The damn thing is going<br>to guzzles amps just in transforming the power to the motherboard at a<br>level well above that needed.  <br><br>I know there is always the option of using purpose-built thin clients<br>with low-power needs. However, what do you do with that old PC?  One<br>option I'm looking at is taking out the old power supply and installing<br>a fan-less power adapter that only gives a 40W output max (from Morex -<br>fully ATX compatible with the!
 cabling plugging straight into the<br>motherboard).  This will not only be quiet but should saves heaps of<br>power.  Additionally, if you have a 450-800 MHz CPU and slow it down to<br>233-300 MHz or so, you should be able to remove all fans from the case<br>after you gut everything else from inside.  Or, am I barking up the<br>wrong tree with that idea that I'm about to experiment with?   <br>-- <br>	Regards,<br><br>	Gavin Chester<br><br>	<br><br>_______________________________________________<br>K12OSN mailing list<br>K12OSN at redhat.com<br>https://www.redhat.com/mailman/listinfo/k12osn<br>For more info see <http://www.k12os.org><br>

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