why are such powerful PSU's recommended...

[Giraffe]

Hi

I know everyone says you will need a powerful PSU with over 50A on the +12V rails for a Dual 8800GTX system

but in this article they run a quad core system with dual 8800GTX's on a 500W PSU with 30A on the +12V rails
http://www.theinquirer.net/default.aspx?article=36066

I know people running an overclocked 8800GTS system on a 450W Antec SmartPower 2 system fine

I read an article from xbitlabs saying under a load an 8800GTX will use a max of 150W(12.5A)
http://www.xbitlabs.com/articles/video/display/gf8800_11.html

that means Dual 8800GTX's will draw ~25A from the +12V rails right?
and there is no way a standard C2D system will use over 25A excluding the Video card, so why are PSU's with ~55A or higher recommended?

 

[sweetpants]

Hi

I know everyone says you will need a powerful PSU with over 50A on the +12V rails for a Dual 8800GTX system

but in this article they run a quad core system with dual 8800GTX's on a 500W PSU with 30A on the +12V rails
http://www.theinquirer.net/default.aspx?article=36066

I know people running an overclocked 8800GTS system on a 450W Antec SmartPower 2 system fine

I read an article from xbitlabs saying under a load an 8800GTX will use a max of 150W(12.5A)
http://www.xbitlabs.com/articles/video/display/gf8800_11.html

that means Dual 8800GTX's will draw ~25A from the +12V rails right?
and there is no way a standard C2D system will use over 25A excluding the Video card, so why are PSU's with ~55A or higher recommended?

To be quite honest I don't know... and this is just my opinion... but...

I would use your best judgement in these situations. It's okay to go overkill in a power supply. It won't hurt anything. If you're going overkill? Go modular, that way you don't have a rats nest of cables. But as for "55 A on the 12V rails blah blah blah" just get what you know you need, and bump it up a tad so you're not taxing the PSU.

 

[mrmez]

From what ppl say, PSU requirements are the most overstated of any pc component by FAR.

But its a good point to remember that the closer to the limit your psu runs, the hotter it gets and less efficient. So to have a psu die after a year or so and possibly kill your 6800 or 8800gtx for the sake of $30 or so... why risk it.

Its like building that 600bhp engine and running low octane fuel. Sure it WORKS... but its prob not a good idea.

Theres also the practise of 'up sell'. Oh no sir... the 8800gts is good, but if you really wanna hit those FPS in Pac Man, get the GTX. Its only $xxxx more!

Then theres Antec* paying Nvidia* (*=insert any brand name here) $$$ to recomend their 50,000w psu for 8800's.

 

[JAYDEEJOHN]

Head room, aging, upgrades etc

 

[sweetpants]

From what ppl say, PSU requirements are the most overstated of any pc component by FAR.

Its like building that 600bhp engine and running low octane fuel. Sure it WORKS... but its prob not a good idea.

eh... that insinuates that you HAVE to have overkill to perform as it should. This isn't true. You end up with people buying 220 dollar power supplies when the 150 dollar was work just as well.

 

[sailer]

Yes, he managed to get it to run, for two days even, but what would be the long term life? The psu components start to age and not put out as much power, then its all down the drain.

Kind of like my old race car. It would run 7000 RPM max, but it would last a whole lot longer at 4000 RPM. Things wear out fast at maximum useage. Of course, that's why I had to rebuild the engine so often. Real bad things happen when it suddenly gives up.

Same with a psu. You can run it at max all the time, but it wears out faster and there's no room for any problems. The author judged 3DMark as stressful, but I don't think that's all that stressful on the psu. He ran it for 2 days. Fine, but what about 2 months, or 2 years? 3DMark runs for about 10 minutes. What if you're in a game for 2 hours that is keeping the power draw to the max constantly?

Ok, just because something can be done, doesn't make it a good idea. And that is why I don't think an article like this is responsible. How many newbies will read it and then stick with their tired 3 year old psu's and then wonder why things don't work? Then the psu will get unfairly blamed for ruining the expensive new components. And really, what sense does it make that someone puts out 1000-2000 dollars on a new build and then refuses to spend 150 dollars on a new psu? It just doesn't make sense to me.

 

[sweetpants]

You can run it at max all the time, but it wears out faster and there's no room for any problems. The author judged 3DMark as stressful, but I don't think that's all that stressful on the psu. He ran it for 2 days. Fine, but what about 2 months, or 2 years? 3DMark runs for about 10 minutes. What if you're in a game for 2 hours that is keeping the power draw to the max constantly?

When do you stress your system for 2 months or 2 years straight? It may not be stressfull, but it I'm sure 3DMark puts a load on your devices, maybe not your hard drive and optical drive. But definately taxes others.

What if you're in a game for 2 hours that is keeping the power draw to the max constantly?
Yea what if? Tell me what a 500W power supply will do under load with an SLI system, just like what the author of that article did.

 

[Trunkz_Jr]

What kinda PSU then would you reccomend if you had a $3000 system Cause i'm about to bulding a new system and i was gonna get the OCZ 700wt but now im starting to think about getting their 850.

 

[cb62fcni]

The 700 should be just fine. Here's the deal, as others mentioned, running a PSU at max capacity stresses the internal components and will likely lead to a premature failure. Also, many PSU's have maximum efficiency below 100% load. I.E. a PSU with a 75% load is more efficient than one that is maxxed out.

 

[sailer]

What kinda PSU then would you reccomend if you had a $3000 system Cause i'm about to bulding a new system and i was gonna get the OCZ 700wt but now im starting to think about getting their 850.

I'll venture a reply here. I recently bought a ThermalTake 700wt in anticipation for a new DX10 video card and some other components. Unless you're planning on SLI with some heavy duty overclocked cpu and other power hungry hardware, you probably won't need the 850wt. I'd suggest that you use a power calculator to gauge your system, and then I'd suggest getting a slightly larger psu then recommended so you have room for future upgrades

 

[Trunkz_Jr]

Well i was also gonna get the Intel Core 2 Extreme. probably gonna spend $3600 cdn overall on a new cpu so I wouldnt really want it to die after a year. One time my friend decided to buy these cheap ram coolers for my ram, it ended up frying my system x_X

 

[sailer]

You can run it at max all the time, but it wears out faster and there's no room for any problems. The author judged 3DMark as stressful, but I don't think that's all that stressful on the psu. He ran it for 2 days. Fine, but what about 2 months, or 2 years? 3DMark runs for about 10 minutes. What if you're in a game for 2 hours that is keeping the power draw to the max constantly?

When do you stress your system for 2 months or 2 years straight? It may not be stressfull, but it I'm sure 3DMark puts a load on your devices, maybe not your hard drive and optical drive. But definately taxes others.

What if you're in a game for 2 hours that is keeping the power draw to the max constantly?
Yea what if? Tell me what a 500W power supply will do under load with an SLI system, just like what the author of that article did.

Fine, and the author himself admitted that he would be more comfortable with a 600wt psu, getting a more peaceful night's sleep as he admitted. He also said "If you have a large RAID array, plus a physics card, by all means go for a 700wt psu." Some of us have more hardware than the system he used.

I currently have 3 computers, one of which is highly stressed at times for days on end. The last thing I need is to have it deep in modeling and then to have it power off or fail entirely because I got cheap on the psu. Fifty dollars saved on a 500wt psu instead of a 700wt would suddenly become pretty stupid at a time like that.

 

[Lionhardt]

coolio

 

[sailer]

Well i was also gonna get the Intel Core 2 Extreme. probably gonna spend $3600 cdn overall on a new cpu so I wouldnt really want it to die after a year. One time my friend decided to buy these cheap ram coolers for my ram, it ended up frying my system x_X

$3600 cdn? Makes the case even better. What would be the rational in spending that much money for a system and then trying to go cheap on a psu? Just top prove that it can be done? Just have a crying towel handy if the thing shorts out and fries all the new hardware. I tend to go on the safe side and buy a bit bigger than required. Its money well spent for my peace of mind.

 

[Giraffe]

so if the Dual GTX, Quad Core system runs on a PSU with 30A (just)

so a single 8800GTX, C2D system should comftorably run on a PSU with 30A?

 

[sailer]

so if the Dual GTX, Quad Core system runs on a PSU with 30A (just)

so a single 8800GTX, C2D system should comftorably run on a PSU with 30A?

Couldn't tell you for sure. It would depend on the total amount of hardware you're running. By the example you give, the obvious answer is yes, but remember, that 30A isn't just feeding the video card and cpu. Its also feeding the motherboard, ram, hardrives, water pumps, and anything and everything else that is in the machine. That's why its best to figure out the total wattage needs of the entire system on a psu calculator.

Mpilchfamily can explain all this better than I can. A good thing to do is to go into the forumz and look up the sticky he did about psu's. Its under PSU 101, as I remember.

 

[sailer]

Forgot about the ram being on a different rail. Sometimes I need to think more before I write.

 

[GeorgeH]

According to one manufacturers specs dual 8800s require only 11amps @ 12v for the 2 6 connector plugs and another 11amps @12v on the bus.

That is about 250w. I expect actual power requirements are less.

Add on an Athlon64 X2 system and the total is under 400w full load.

A 500w power supply should power such a system forever.

 

[corporal_linko]

Good link to check out, I don't know how acurate but it should get you in the ball park.

http://extreme.outervision.com/PSUEngine

 

[jaguarskx]

I read an article from xbitlabs saying under a load an 8800GTX will use a max of 150W(12.5A)
http://www.xbitlabs.com/articles/video/display/gf8800_11.html

According to Xbitlab's article, nVidia estimates the 8800GTX's power consumption will be 145.5w. Xbitlabs has not made any power measurements of the 8800GTX yet because the modified motherboard that they use to measure GPU power consumption is not compatible with the 8800GTX.

On the bright side of things, nVidia's power estimate of the Geforce 7950 GX2 is 143w, while Xbitlabs measured 110w. Therefore, it is possible that the 8800GTX will actually draw less than 145.5w.

Using SLI (or Crossfire) doesn't necessarily mean that double the power will be drawn. I suspect it will be less because I really doubt both GPUs will be stressed to the limit. That's just an opinion though until Xbitlabs can modify a SLI mobo for such power measurements.

 

[sailer]

As a bit of a side issue, I saw released power figures for the new ATI card, the R600: www.vr-zone.com/index.php?i=4622 . At 270wt, one of these will put a big dent in whatever a psu puts out. Two of them would really be demanding. Even given that they might take a bit less power, as shown by the Nvidia 8800 not taking as much power as advertised, these cards are power hungry monsters that will make a big psu even more of a necessity.

 

[El_Hefe]

Its like building that 600bhp engine and running low octane fuel. Sure it WORKS... but its prob not a good idea.

Theres also the practise of 'up sell'. Oh no sir... the 8800gts is good, but if you really wanna hit those FPS in Pac Man, get the GTX. Its only $xxxx more!

bwhahahaha!!!!