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Which PSU?

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July 23, 2006 7:46:51 AM

Hoping to get some opinions here. Here are the two PSUs I am looking at for my next rig -
Antec TRUEPOWERII TPII-550 ATX12V 550W
SILVERSTONE SST-ST50EF ATX12V 500W

By this site - http://www.extreme.outervision.com/psucalculator.jsp I only need 413W maxed out, no O/C.

My build (basically):
Asus P5B
Corsair DDR2 800 2GB
Radeon X1900 XT
Seagate 3G 320GB HDD
DVD burner
2 LED Fans
Fan Controller
UV Cathodes x2
E6600 CPU

I added a second HDD and second IDE optical drive in case I ever go that route, as well as 4 USB devices (never know). After all that, I have 85W left over.

Question is this - between those two, is higher efficiency better (Silverstone) or more power better (Antec)?

More about : psu

a c 158 ) Power supply
July 23, 2006 8:44:53 AM

Either of those should be more than enough to run your rig. I'd go for the least expensive of the two.
July 23, 2006 11:10:04 AM

Both are solid PSUs with dual 12 rails with high amperage across the rails. Both companies have good reps so you need not fear dependability. Only difference here (besides the 50 watt advantage for the Antec unit) is that the Silverstone is $12 cheaper. You would do fine by eaither one.
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July 23, 2006 12:38:58 PM

Why don't you go for the Antec NeoHE 550w that I recently bought?

It's $10 more than the TruePower but offers the higher efficiency (80-85% dependent on load vs 70% on the TP)...

Plus its quieter.

You've also forgotten efficiency in your calculation...

The 550w truepower, for instance, would actually provide 385w of power at 70% efficiency, vs 467w at 85% efficiency on the NeoHE 550w.

Both, however, are rated as SLI capable by Antec - so in a real-world scenario should be able to cope with all but the most drive-laden, overclocked Athlon FX / dual 7900GTX setup.

For the noise level, though, the NeoHE has my nod.
July 23, 2006 12:48:31 PM

Silverstone = $87
Antec NeoHE = $118

Somehow that dont look like $10 to me. But thanks for the idea, maybe if it drops $30 it will be an option. Otherwise, at that price range, there are a lot more options open to me.
July 23, 2006 12:58:32 PM

As I stated I was comparing it to the Antec, TruePower, which in the UK is only £5 ($10) cheaper than the NeoHE version in the UK. As has already been stated the Silverstone is cheaper still.

If you don't have the extra cash to pay for a quieter PSU (I'm fussy) then I'd take the advice above to go for the Silverstone. Personally I don't like the lower efficiency of the Antec TruePower series.

I also presume you don't pay your own electricity bills? An 85% efficiency PSU will use 60w more than a 70% efficiency PSU at 400w load.

If you add up the electricity costs of running an additional 60 watt lightbulb every time you switch on your PC, then you'd have paid for the $10 price difference for a better Antec PSU within a year in waste alone.

'nuff said.
July 23, 2006 1:22:07 PM

Sorry, using US prices, the Antec is only $89 atm. Still a solid $29 less than the Neo.

Well, guess I should start by saying I dont pay for electricity. So is the 550W with a worse efficiency only for the power coming INTO the PSU, not out to the components?

I had thought efficiency of power related to the output to the components of the computer.
July 23, 2006 2:04:05 PM

The more obvious problem with a lower-efficiency PSU is the cap for supplied power is lower than the stated output of the psu.

However, the reason that power supplies have an efficiency lower than 100 percent is because of energy they lose that is not fueling your components (the main reason, in heat).

It is impossible to destroy energy, only for it to be converted to another form.

This is also why quieter/fanless PSU's need to have a high efficiency, to keep within thermal requirements. The Phantom fanless antec CPU for example offers 85% at full load, vs 80% full load efficiency on the NeoHE.

Anything that is inefficient is wasting electricity. For example, standard incandescent bulbs waste a massive amount of the wattage they consume in heat.

But yeah, I'm sorry that the pricing difference is more in the US :( 
July 23, 2006 2:43:11 PM

Quote:
Hoping to get some opinions here. Here are the two PSUs I am looking at for my next rig -
Antec TRUEPOWERII TPII-550 ATX12V 550W
SILVERSTONE SST-ST50EF ATX12V 500W


In that price range, be sure to check out the mushkin. It is 550 watts also, but has the ability to fuse its two 12V rails to provide extra current capacity under a large load. Excellent quality PS, quiet fans, good efficiency.
July 23, 2006 3:10:54 PM

i'd recommend the Truepower 550w. or the muskin clue less posted.
July 23, 2006 8:34:12 PM

Quote:
Leaving yourself with only 85watts of maximum headroom is ok but the more a ps is loaded, the less efficient it is. I'd go for a 600 and have a little headroom for video upgrade later on.


For sure. I tend to go well beyond what many people here advise but I like to be on the high efficiency portion of the efficiency vs. load curve and also like to keep the PS temps low. For the same reasons, I like cases with blowholes. A while back, I disabled the blowhole fan and covered the blowhole port on my Armor case that has a 4400+. The idle temp of my PS went up ~3C, load went up 5C. Anyway, ever since I first read of the expected power requirements of DX-10 cards, I've been adding another 100 watts of headroom to the stuff I build.
July 24, 2006 4:47:04 AM

Quote:
Leaving yourself with only 85watts of maximum headroom is ok but the more a ps is loaded, the less efficient it is. I'd go for a 600 and have a little headroom for video upgrade later on.


Except the Mobo only has one PCI-E card slot. I doubt I will be upgrading from an ATI X1900XT anytime soon. Even with the addition of DX-10, the software to exploit the capability will be lagging - as hardware always moves faster than the software to use it.
July 24, 2006 9:11:54 AM

Froogle FSP Epsilon 600W >85% effinciency... I got it got 109$ from ewiz and it seems to be the better deal!
a c 158 ) Power supply
July 24, 2006 2:26:02 PM

Quote:
Leaving yourself with only 85watts of maximum headroom is ok but the more a ps is loaded, the less efficient it is.

Incorrect statement. PSUs typically are most efficient above a 65-70% load. Take a look at some of THG's PSU reviews, they do an good job of giving efficiency at different loads for the PSUs they test.
Quote:
I'd go for a 600 and have a little headroom for video upgrade later on.

Taking the above into account, it is good to have headroom in your PSU, but it is less efficient in a light-load condition. It is better to balance system expandability with system loading/efficiency. While you're juggling those two, you need to remember that the average system load is nowhere near the maximum load - even when stressing one portion of the system with a benchmark. Most PSU wattage calculators are designed to give you the theoretical maximum power draw for the components that you enter - a power draw that you are not likely ever to reach. Read this interesting article at Sysopt.com - running two complete rigs on one PSU in order to draw enough power to stress the tested PSUs!
July 24, 2006 3:00:47 PM

Here is an interesting review that a site, Bytesizedreviews, did on different brands of PSU's in the 500 - 600 watt range. It shows stability over the 12v rails and variances that each brand displayed under load (which should be of interest to you) across their respective voltages (i.e. 5v, 12v and 3.3v).

http://www.bytesizedreviews.com/?rev_id=302

According to their testing Enermax, Seasonic and Silverstone were the most stable.
July 24, 2006 3:37:12 PM

Quote:
Why don't you go for the Antec NeoHE 550w that I recently bought?

It's $10 more than the TruePower but offers the higher efficiency (80-85% dependent on load vs 70% on the TP)...

Plus its quieter.

You've also forgotten efficiency in your calculation...

The 550w truepower, for instance, would actually provide 385w of power at 70% efficiency, vs 467w at 85% efficiency on the NeoHE 550w.
Both, however, are rated as SLI capable by Antec - so in a real-world scenario should be able to cope with all but the most drive-laden, overclocked Athlon FX / dual 7900GTX setup.

For the noise level, though, the NeoHE has my nod.


Please to anyone who reads this, stop making this efficiency mistake... the percentage IS NOT the rated DC output x the efficiency.... IT IS the rated output / the efficiency. Your PSU should always put out the required load, no more no less, it is the amount of AC power that it draws to create that rated DC power which is the efficiency.

If you have a 500w at 70% efficiency then that means it is drawing 714w from the wall (this is at full draw and will not actually pull this much all the time). If you have a 550w at 85% efficiency then it will draw 647w from the wall.

Another example, say at one given moment it is only drawing 300w, then the 500w / 70% model is actually drawing 428w from the wall whereas the 550w / 85% model is drawing only 352w. Keep in mind though that most PSU's are actually the most efficient at around 70 to 80% of full power.

From the above examples you can see that the 550w psu is delivering more power (at full load) to your computer while drawing less (at all loads) from the wall socket, THAT is what is important.
July 24, 2006 5:10:29 PM

I think you guys may have PSU efficiency backwards. Both PSU's should probably put out close to their rated power (since they're name brands), but the efficiency affects how much AC current required to generate the requisite DC current. The higher the efficiency the less input power is "wasted" as heat, noise, etc and the less power is required to generate the advertised wattage.

Edit: Doh! I really need to refresh pages before replying... beaten to it again!

-mcg
July 24, 2006 6:24:09 PM

Quote:
Leaving yourself with only 85watts of maximum headroom is ok but the more a ps is loaded, the less efficient it is.

Incorrect statement. PSUs typically are most efficient above a 65-70% load. Take a look at some of THG's PSU reviews, they do an good job of giving efficiency at different loads for the PSUs they test.

You are both right. The efficiency peak can plateau in the 60 to 80% load range. Outside of that peak, efficiency is lower. This is one reason why I only use a PSU calculator as a starting point. If you estimate that you need 300 watts, I'd recommend getting a 400 watt unit so that your full load efficiency is high. This also means that your PS won't be operating super hot, because heat lowers output. Purchasing a PS based just on a peak load estimate without adding in some headroom is just a one-way street.

Quote:
Taking the above into account, it is good to have headroom in your PSU, but it is less efficient in a light-load condition.


Correct again. But if I had to choose between poor efficiency at either low or high load, I'd pick low load. You are drawing less A/C current at low load, so the efficiency loss means less there than it does at high load.

Quote:
[the average system load is nowhere near the maximum load - even when stressing one portion of the system with a benchmark. Most PSU wattage calculators are designed to give you the theoretical maximum power draw for the components that you enter - a power draw that you are not likely ever to reach.


My kid's game box (single core Opty OC'ed about 30%, 1900XT OC'ed about 10%) consistently runs at a pretty high load when he's gaming. He has pretty much nothing on the box in the way of extras that idle other than the optical (part of the time). The CPU and GPU are his two largest current drains and they run at a pretty good load much of the time. I'm not saying that he's pegging all components all of the time - just that the average use is fairly close to peak. I could rummage around and dig out my measurements but that summary is accurate.
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