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Please help me calculate power requirement

Last response: in Components
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July 11, 2009 6:16:20 AM

I'm trying to figure out how many amps at 12v the system I'm building will require, since it seems like the true limit of basically any

PSU is the amount of power is supplies on 12v rails. I have a PSU that supplies 17A at 12v and I'm hoping that will be enough. The

system is pretty basic:

ASUS M3N78-EM mobo with NVIDIA GeForce 8300 onboard video
AMD Athlon 64 X2 5400+ Brisbane 2.8GHz 65W processor
1 SATA HD
1 SATA DVD-ROM drive
May add one or two IDE or SATA HDs and a TV tuner card down the road

I'm having trouble finding data on how much these devices will draw from the 12v specifically. The CPU isn't hard, since it draws all

its power at 12v: 65W/12v = 5.4A. Let's say 6.5A with imperfect efficiency, though I have no idea at what efficiency I should expect the

CPU to operate. But what about the rest? In particular, I expect the onboard video to draw significant power at 12v, but I can't find

how much.

Can anyone help? And can anyone suggest a resource for finding this kind of information in the future? When I find power usage

information at all, it's usually simply listed in watts, without specifying which rail it's drawn from.

I did find the following two links in thread:

http://www.extreme.outervision.com/PSUEngine
http://web.aanet.com.au/SnooP/psucalc.php

Both seem pretty useful (if a little out of date), but neither site seems to have good information on onboard video.
July 11, 2009 6:26:10 AM

That won't require much power. Something like a good quality 350 or the Corsair CX400 would be more than enough. Onboard video is usually pretty light on the power usage.
a b ) Power supply
July 11, 2009 6:43:24 AM

As long as your unnamed psu delivers what it reads, it should work fine.
Related resources
July 11, 2009 7:37:32 AM

My previous system:

x2 5400+, lite on dvd, wd 640 aaks
780g mb, tv tuner (kworld)
4 gig ram
8800gts 512...all on kingwin 450 watt ps
a b ) Power supply
July 11, 2009 1:14:30 PM

Below is Antec PSU calculator.

http://www.antec.outervision.com/

Nvidia 8300 is one of the option for a GPU. Leave the Video Type as Single Card.


Measuring actual current draw can be done but is not simple....This will be measurements of actual current coming out of your Power Supply...

Watts= I (current in Amperes) x V (Voltage in Volts)

If you want to measure the actual draw on your rail use a clamp Meters. That will give you the actual current on each wire. Attach is an example of Clamp Meter you can use.

http://us.fluke.com/usen/Products/Fluke+330.htm

After that you can use a Digital Meter to measure the voltages. Below are example of digital meters you can use.

http://us.fluke.com/usen/WhereToBuy/Promotions/Digital-...

MEASURE EACH CABLE THEN ADD THE CURRENT FOR EACH CABLE:
When measuring current you need to make separate current measurements for each cables. Say for example you have 2 yellow cables on the Power connector. Measure each 2 cables then add the measurements.

PEAK & AVERAGE MEASUREMENTS:

Semiconductor CMOS devices are known to drive high SURGE-CURRENTS during power -ON or START-UP. You can set your CLAMP-Meters(for Current) to measure PEAK value. Power sequence your PC and you will get the Peak for each cable.

At normal operation disable the PEAK option and you can measure the actual average current draw.

GPU Power Consumption when ACTIVE (~ Playing gamesfor example).
GPU Power Consumption is HIGH when playing GAMES so you need to factor that in when doing your measurement.

Good brand power supplies are rated with 80% efficiency. The 20% are loses in heat(inefficiencies) or use for the internal circuitry of the power supply itself.

Reference information for PS efficiency ratings

http://www.antec.com/pdf/flyers/80_PLUS.pdf
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