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Extreme Power Supply Calculator Crazy???

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February 13, 2008 5:24:10 PM

I was wondering if The calculation of what my power supply needs to be is crazy
Here are my system components: (Still Not bought, just in the planning stages)
Q6600 O.C. to 3600
4gb DDR2 800-1066
EVGA 8800GTS 512MB (Possible OCed)
2 DVD+/-RW
Possibly a Dual BluRay HDDVD Drive
Gigabyte GA EP35 DS3P
Arctic Cooling 7 Pro Freezer
3 Yate Loon Fans
Zalman VF900 VGA Fan

February 13, 2008 5:25:58 PM

Sorry ha ha forgot to add how much power it was thinking of:
1391!!!! freakin A
February 13, 2008 5:45:54 PM

Thats wrong. You are looking at a 620W power supply. That will do fine.
Related resources
February 13, 2008 5:48:01 PM

I did it for your system and adding a couple hard drives and a sound card with a CPU overclock to 3.2 and 20% PSU aging I got 414w. I think you did something wrong.
February 13, 2008 8:02:21 PM

I reckon a 750w will cover it EASILY, so yeah a 620/650 should be good :) 

make sure you have high ampage rails for stable OCes. Though any decent high wattage PSU will have good high amp rails.
a b ) Power supply
February 13, 2008 8:22:48 PM

Did you select 4 CPUs by any chance? Lots of people do that, the interface bites.

Anyway, for that system a Silencer 750W would be plenty (it's on sale for $150 at newegg and $140 at www.buy.com).

Edit: or Corsair 620HX if you prefer modular.

Are you sure you need the VGA cooler? The GTS G92 overclocks nicely without any aftermarket cooler.
a b ) Power supply
February 13, 2008 8:54:51 PM

I ran the numbers based on your parts and I get 478W with 85% System Load and 15% cap aging. 3 SATA HDDs, 1 BD drive, 10 80mm and 4 120 mm (all LED). I recomend you get a Corsair 520HX for that set up. or any top tire PSU listed here:
http://www.xtremesystems.org/forums/showthread.php?t=10...
February 13, 2008 8:58:03 PM

^ agreed the Corsiar620 is a beast and will do that easily
February 13, 2008 9:24:13 PM

aevm said:
Did you select 4 CPUs by any chance?
You beat me to it.
@OP: You need to read the footnotes, where applicable, at the bottom.
February 13, 2008 9:52:56 PM

Hey guys thanks for all the help. Ya so i guess i will go with a 600 ish PSU.
I am choosing from this site that i found ranking PSU's
http://www.xtremesystems.org/forums/showthread.php?t=10...
Any recommendations on overall system setup? how loud is the fan on the 8800 GTS? Thats the only reason i was going to go with an after market cooler
February 13, 2008 9:53:53 PM

ha ha sorry just noticed someone else posted that link
February 13, 2008 10:42:24 PM

This is an old list, last edited on 4-07-2007. I have seen the CoolerMaster real Power PSU's get high marks but they were introduced after 4-7-2007. There may be better PSU's out there that you will overlookm if you go by this list.
February 13, 2008 11:34:45 PM

I once had a nice little conversation with a guy who actually designs power supplies and other electrical equipment for the aerospace industry. His clients include NASA, Lockheed Martin, and the like. He set my straight on a number of misconceptions about PSU's in the computer industry.

1. Sales, sales, sales. Power supply companies want to scare you into buying more power than you need because that way they can sell their more expensive (and you better believe higher $$$ margin) PSU's. Other component manufacturers also seem to scare consumers into buying rediculous power supplies. Video card manufactureres are at fault here,...although they are just covering their own asses in making sure people don't try to upgrade their 250watt Dell desktops with an 8800GTX and wonder why it don't work.

2. A PSU is "happiest" running at approximately 80% of it's total capacity. What does that actually mean? That's where it's most efficient, and will actually COST YOU LESS! That's right, I actually tried this test myself. I have a P4 2.66Ghz, Supermicro Socket478 Server board (7230) with 4 sticks of DDR400 RAM and 6 HDD's (4SATA, 2IDE). Running the stock 550watt Antec TruePower PSU that came in the Titan case actually drew more wattage from my UPS then a 350watt Antec Smart Power! Why? Because it was being waaay under-utilized. The 350watt also ran cooler because it was more efficient. (efficiency is basically a measure of how much energy is lost in a transition from one form to another. In this case electricity is lost as heat as it is converted).

3. Based on the exact components you described I think any more than 500watts is overkill. As a matter of fact, a 500watt PSU should be fine if you get 2 8800GTS's and 2 HDD's for RAID!

4. If anyone can come up with info to the contrary, I would be more than happy to listen...I mean hey...I only got my info from a guy who designs power supplies for outer-freaking-space...he's probably just a high school drop-out who doesn't know anything. :kaola: 
a b ) Power supply
February 14, 2008 12:10:14 AM

@OP: Get a Corsair 520HX/620HX depending on if you plan to SLI (620HX for SLI)
a b ) Power supply
February 14, 2008 12:12:48 AM

hcforde said:
This is an old list, last edited on 4-07-2007. I have seen the CoolerMaster real Power PSU's get high marks but they were introduced after 4-7-2007. There may be better PSU's out there that you will overlookm if you go by this list.

That list is pretty recent (a bit outdated, but still a good list). Those PSU listings are pretty much the best/accurate listing on the web.
a b ) Power supply
February 14, 2008 1:44:03 AM

CRush1682 said:

1. Sales, sales, sales. Power supply companies want to scare you into buying more power than you need because that way they can sell their more expensive (and you better believe higher $$$ margin) PSU's.

2. A PSU is "happiest" running at approximately 80% of it's total capacity.


1. Absolutely true. It costs them very much the same to make a 500W PSu and a 750W PSU, so of course they prefer to sell the more expensive 750W version more.

2. Well, it depends. First of all, modern good PSUs are supposed to deliver over 80% efficiency at all points (20%, 50%, 100% load, etc.) Second, my own PSU, which happens to be pretty good by the way (Anandtech's PSU of the Year 2007), is happiest around 40% according to this chart here. I've seen plenty of similar charts for other PSUs, not just the Silencer. I guess your expert defines "happy PSU" in a different way than me, i.e. he wasn't talking about efficiency. Ask him to clarify please. I don't think he was talking about noise either, because lots of PSUs are quiet at lower loads but by 80% their fans are already getting excited and making silly noises.
http://www.anandtech.com/casecoolingpsus/showdoc.aspx?i=3040&p=11
http://www.anandtech.com/casecoolingpsus/showdoc.aspx?i=3040&p=16
February 14, 2008 3:24:00 AM

I was going to respond to him, but I figured I'd just wait.
February 14, 2008 4:12:40 AM

rkowalk said:
Hey guys thanks for all the help. Ya so i guess i will go with a 600 ish PSU.
I am choosing from this site that i found ranking PSU's
http://www.xtremesystems.org/forums/showthread.php?t=10...
Any recommendations on overall system setup? how loud is the fan on the 8800 GTS? Thats the only reason i was going to go with an after market cooler


Sorry, I'm a little late on this. The stock fan isn't that loud at all. Stock speeds, I can't hear it at all, at 60% where I put it when I'm playing games with my OC, it's just BARELY audible over the rest of my system (most of which comes from my cpu cooler). I'd stick with it...
February 14, 2008 4:35:26 AM

CRush1682 said:
2. A PSU is "happiest" running at approximately 80% of it's total capacity. What does that actually mean? That's where it's most efficient, and will actually COST YOU LESS! That's right, I actually tried this test myself. I have a P4 2.66Ghz, Supermicro Socket478 Server board (7230) with 4 sticks of DDR400 RAM and 6 HDD's (4SATA, 2IDE). Running the stock 550watt Antec TruePower PSU that came in the Titan case actually drew more wattage from my UPS then a 350watt Antec Smart Power! Why? Because it was being waaay under-utilized. The 350watt also ran cooler because it was more efficient. (efficiency is basically a measure of how much energy is lost in a transition from one form to another. In this case electricity is lost as heat as it is converted).


Comparing two different models of PSU isn't a valid test. Yes when all else is equal the smaller capacity unit might be more efficient but it depends a lot on what wasn't upgraded versus the higher wattage model. With very similar models there is a modular nature such that many parts are the same just some key component changes.

You should not try to run a PSU at 80% of rating even if the PSU is honestly rated. The reason is longevity, PSU aren't built towards extreme budgets and a PSU designed capable of handling more current (all else equal) tends to have better heatsinking and/or airflow, lower impedance capacitors to yield longer life and lower ripple, and overall more robust design in any area close to it's limits.

If your system is using 80% of, let's say a 350W PSU since that was the example previously, and that PSU were 82% efficient, then we have (0.8 * 350)/.82 = 341W total power consumption.

Next let's suppose another modern 80-plus PSU but the 500W model, this time it's barely making 80-plus due to running at only (.8 * 350) / 500 = .56, 56% capacity.

So then for the 500W PSU it's (.56 * 500) / .80 = 350W total power consumption, only 9W more than the 350W PSU and only 9/350 = 0.025 or 2.5% more power.

That minor difference in power has to be weighed against replacement cost when the 350W fails earlier, because it will fail earlier if all else is equal. If we wanted to be green about it, that also means more manufacturing pollution to build a 2nd PSU to replace the first, and landfill throwing away the failed PSU. Most (consumer grade, PC) psu running at 80% load will not last the life of the system.

In an idea world, and maybe at Nasa when cost is no limit, things are different than in the consumer products seen in the PC industry. Even a PSU like you'd find in a $20K copy machine is vastly superior to what's in a PC when it comes to build quality, and certainly not as good as you'd put on a space probe. The manufacturers are rating for peak power at unreaslitically low ambient temps except for a small handful, if your PSU says it can handle 350W at 20C ambient temp, you're looking at having a colder than normal room in order for the PSU intake to be at 20C inside a case with other parts producing (as per the example, 350/0.8=) 280W.

CRush1682 said:
4. If anyone can come up with info to the contrary, I would be more than happy to listen...I mean hey...I only got my info from a guy who designs power supplies for outer-freaking-space...he's probably just a high school drop-out who doesn't know anything. :kaola


What he may not know is about the actual differences in PSU available for purchase. Given this info and test data as he runs on his designs, his conclusion would not be as quick and simple as your summary. There are always tradeoffs and one is how much power is saved as we aren't running from battery power and solar cells, for instance.

The requirements for a power supply in outer space are different as is the goal to build supporting power for millions to billions of dollars worth of equipment. He also has no need to design for an overclocked processor and video card, he never has anything as demanding from an extremely cost contrained build budget. NASA/etc don't run anything that only peaks at 300W or so power consumption but can have the requirement for as fast a power state transistion as an overclocked Quad Core Duo and a gaming video card. NASA was using 80486 processors for a lot of their critical stuff the last time I heard, and with good reason that a very robust PSU can be built using small solid caps in the PSU instead of having electrolytics drying out in space and subject to more temperature sensitivity. Beyond processors and equivalent logic, nothing else has a requirement for that fast a transition in current or else it will crash.

It's really apples and oranges, he may be great at what he does but that doesn't mean he could work magic given $15, some string and some glue (kidding about string and glue but really there are always corners to be cut arriving at PSU with desirable prices, if it can't hit a desirable price point the volume sold goes through the floor and the price has to rise very quicky to make it a profitable venture for manufacturers. That's why a 750W PSU costs so much more than a 300W, as the parts differences certainly aren't accounting for a typical tripling in retail selling price.
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