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Anandtech debunks power supply myths


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I feel guilty for buying a brand new power supply for my 4870, just because I couldn't wait another day for a molex-PCIe adapter to come in to Microcenter.

 

It cost me $100. :(

 

Cost me $300+ to buy this damned PSU, because I wanted a 8800GTX SLI, geez something half than that would be even better..

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If I don't make people look at their purchases with utter contempt, then I am not doing my job.

 

I got this PSU: http://www.newegg.com/Product/Product.aspx...N82E16817171023

 

The funny part is, it turns out that even my lowly 500w power supply would have been more than enough, since I modded my 4870's voltage, so it uses significantly less power, and runs cooler with the stock speeds of 800/950. Microcenter also got a shipment of molex-pcie adapters in that very same day, but I didn't care, because I had my 4870 running.

Edited by brandon
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Well, I don't usually get into this debate. I spent 6 years as an electronics tech in the

service and with honeywell. 35 years in electical as employee and employer.

 

For the most part, the PSU power consumption you read are garbage.

The problem is with the product. Does it work efficently.

You can normally deduct 20% off load for normal, and 30% off load for efficent.

 

I run a 3850 cross fire, E6700, 2 sata HDs, DVD RW, 2 gigs, etc, on 550 watts, and

no voltage drop.

 

But I do not load any extra programs, turn off all windows security items, etc etc.

Have nine machines this way, and no problems for over five years.

 

My wife is still on a 631, and she won't let me put a 6700 in its place,

Already loaded, to how she likes it. If it ain't broke, don't fix it. Just

build it right the first time.

 

Well to each their own.

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cant say i read the article but then again my 900w Tagan has been goin strong for almost 3 years. tisk tisk Brandon,you couldn't wait one day. then again it could be for bragging rights. '' hey check out my new 1300w PSU it only cost me 300$, hey ya got a twenty i can borrow till next payday'' :P

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i didn't have any actual data to back up my opinion, but since rosewell came out w/ some solidly rated single 12v rail psu's, it's all i've used to build with as they were roughly half the price of say, an Antec unit.

 

this just backs up my opinion that 1k units really aren't needed, and that for most people, a 500 watt unit would work wonders

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I buy a good PSU (not extreme) because of stability more than anything.

 

They kind of skim over saying overclocking doesn't add much load but things can add up quickly if your upping voltages. Just the CPU for instance

 

10 % OC will be about 10 % more power

20% OC will be about 20 % more power

40% OC will be about 40% more power

 

10 % OC with 10% volts increase will be about 21% more power

20% OC with 20% volts increase will be about 40% more power

40%OC with 20% volts increase will be about 80% more power

80%OC with 20% volts increase will be about 160% more power

 

That 80% OC with a 95W CPU is now drawing 142W. For the real extreme people who are on phase they can easily get this figure up to 200-250W. Now add up 250+W each for 4 overclocked GPUS and its alrady 1.2+KW without even adding up drives, MB, etc. Don't forget how much electricity for the compressor ;)

Edited by ewitte
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Wattage increases are logarithmic once voltages are increased, not linear. An 80% increase in clocks alone, with no voltage increase would make the TDP of a 65w processor ~117W. Now, throw increased voltage into the mix, it would be more like 188w, if my calculations are anywhere near correct.

 

Here's what I did to get the numbers: I used the 65w TDP as an example, and with perfect linear scaling with no voltage increase, along with an increase of 80% in clockspeed, I got 117W.

 

To figure out how it scaled with voltage, I basically divided the TDP of the processor by the voltage it uses (1.325 in my example), which gave me approximately 49A. I then multiplied that by 1.45v, which gave me 71w. And by adding those two figures together, I got 188w as a TDP.

Edited by brandon
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