I'm about to go SLI with an Antec Phantom 350w

That's a lot of kit to run off 350w. I think it could work through the magic of television but back here in reality...I highly doubt it. But let us know how it works out for you.

Heh...I think you will be buying a bigger PSU after this is all done. It will be interesting to see what happens.

No matter what happens... that is one cool looking power supply! So in a way, you're a winner regardless

It would probably be ok with a standard-ish system of one HD, one optical, an extra card or two like the soundcard and some fans. But there are extra HDs and watercooling too, I assume the pump is powered from this PSU. It will be close hopefully nothing goes might want to move some things onto the 12v1 rail if that's possible.

voodoomelon said:

...however the 7900GSs do use a fair bit more power than his 7800GTs.

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Not really. 7800GT vs. 7900GT.
I'd say you'll be fine. On the edge, but fine.
But, as Oklahoma Wolf said, take a look at capacitors and you'll need a very good airflow around the PSU.

Watercool the PSU too. Add it to the loop. I gaurantee it will perform much better Haha better have no leaks though

GS is an undervolted GT, I would assume equal or less power usage.
So when are you going to fire it up? (I say this because well, he said he's going to do it sooo no point arguing with him)

voodoomelon said:

Efficiency has got plenty to do with how many components the PS can run at any one time.

If you have some piece of crap 350w PS with a 70% efficiency rating, then nearly 1/3 of the power being drawn from the wall is being lost to heat and hence is not going to the PC components.

However, if you have a very high efficiency PS like my Phantom, a mere 12% is being lost to heat. That's a difference of 18% efficiency, which equates to 63w extra output by the Phantom.

Of course there are other issues involved, but there is a sizeable difference.

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You're wrong there, as I explained in the bit you quoted. A 350W PS doesn't draw 350 from the wall and then loses some to better or worse efficiency. It draws whatever it needs from the wall to get to its specified 350W output (whether it actually puts out what it is specced for is another matter btw), so a more efficient PSU needs to draw less power to get there, a less efficient one draws more. That doesn't affect the power delivered to the components.

Alexhk is saying the same thing in his post, here:

Alexhk said:

Do something for me, look at the label on your power supply. Notice that what is being listed is it's rated output wattage and amperage. Not the input. If you have two 350 watt power supplies that can actually handle a 350 watt load then they will both output 350 watts regardless of their efficiency. Efficiency will be seen in how much power each PSU draws from the wall to output 350 watt. If one power supply is 80% Efficient at full load it will draw about 437 watts while one that is only 65% efficient at full load will draw over 535 watts to reach its 350 watt output. So obviously the less efficient power supply is creating truck loads of extra heat which isn't desirable but both power supplies can still output the same 350 watts or power. All that extra heat in a less efficient power supply can lead to an early death if cheap capacitors that can't handle high temperatures are used, ala antec smartpower units.

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Also note that even though the generation of heat may affect component life, this is heavily affected by the cooling system of the PSU. A tornado fan in there will take care of heat handily, whereas a passive supply will have problems. That's also why Antec wants the Phantom to generate as little heat as possible-- it cannot shed it very well because it has no active airflow.

nvidiaOCmaster said:

It will work fine. That im sure of. I saw a display case at a computer show running quad SLI on a 350W PSU and it was working fine.

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I saw a man pulling a truck the other day, I'm sure you'll do fine too...

Efficiency does play a part in the power your PSU can deliver, though.

Simply because a less efficient PSU must create more heat - and more heat means more resistance to the flow of electricity.

According to PC Power & Cooling, that can add up to a loss of nearly 10% in the worst cases. Also, PC P & C state that many PSU's have inflated power numbers which could only result if the unit were working in 25C temperature, instead of the normal working temp found inside critical units of the PSU. So that can also lead to another 10% drop in power capacity.

It's a beautiful pic on that Antec passively cooled PSU, but I question the logic behind it. I have two Antec 450 PSU's within arm's reach of me - and I can't hear either one of them. These are in Sonata II cases, and the only thing you can hear (slightly), is the tri-cool case fan on it's low setting - barely. Frankly, I look for the front case light just to see if it's on when I'm not using the monitor or keyboard.

Now that's quiet - but that's the trend with the active PSU's. The Seasonics, the PC Power and Cooling "Silencer" series, the Antec's latest PSU's, the "noise taker's", etc. They've got it figured out that the consumer wants a quiet PC, and they know what was making the noise (waves of air pressure hitting the exhaust fan of the PSU), so they just re-designed the interior space a bit, and added a mechanism to speed up the fan in the PSU only if the heat required it. The exterior Antec PSU fan usually doesn't even move, even at 100% full cpu utilization (folding proteins for FAH). The 610 Watt PC P & C "silencer" fan does move - but you can barely hear it even in a quiet room.

When I first got my SLI boards, I went to the ASUS and ABIT forums. Lots of complaints about "my new mobo won't boot up", "it boots, but randomly resets while I'm gaming", etc. A large number of these problems were traced to psu's with less than 400 watts, not able to handle the load of an SLI system.

I'd recommend the OP to consider one of these larger capacity power supplies. Consider that a cooler-running power supply will last a great deal longer than one that is forced to run hot. In the case of a psu, this could amount to YEARS, of extra life before failure, not just a few weeks or months.

For efficient air cooling, you NEED fans (note how few cars do without them in front of their radiator), and those fans today, can be VERY quiet. Extra heatsinks on the exterior casing just aren't nearly as good.

Adak

A watercooled PSU is silent AND cool. NOBODY LISTENS TO ME ^_^

Wow, great, lots of info there, thanks for the lecture on efficiency, cleared a lot of things up.

Well, i'm typing this on the system in question, it's been sitting in Windows now for about 3 hours, 2 watercooled 7900GSs installed and both running at a cool 19*C.

HOWEVER:
My backup 200GB Maxtor went POP!

Now, first impressions would be that the PS was the culprit, but I don't think it was. First of all, the PS wouldn't overload a hard drive, it would be the opposite. Second, I installed the Maxtor on the same rail as a 120mm fan that is running off a 2 meter cable (and has been doing so for a year now). I believe this may have contributed to it blowing. And third, I know four people who have had their Maxtors pop and have sworn never to buy them again.

My RAID 0 is fine, and everything is running perfect. Only thing left to do is run a game and to cry over the fact that I lost a sh*t load of data...

The PS seems to be buzzing fairly loudly, I only noticed it when I had my head against the back of the case.

The unit was getting quite hot, which it has been before, so i've placed an 80mm fan at the front of the PS blowing through and out the back of the PS.

Damn its loud by my standards, I've only have one 120mm fan rotating at a literally silent 500rpm in my case for the last year.

The buzzing could be coming from loose windings on a transformer

Anyway Have you tried stressing the system yet? Sitting in windows is good news but the real test is in a 3D game where you have your CPU, both video cards and sound card drawing full tilt. Good luck

First of all...

nvidiaOCmaster said:

It will work fine. That im sure of. I saw a display case at a computer show running quad SLI on a 350W PSU and it was working fine.

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Yeah right =P


Nvidia recommends 26-28 amps for 7900gs sli. You've got 34, so it will definitely work, just a question of how long. It might overheat like others said, so maybe you could put a fan on it. Or you could get a dedicated video card power supply (like this http://www.hardwarehounds.com/techspotlight/powerexpress.shtml) as a cheaper way of upgrading the psu.

I like your water cooling setup btw.

PaciFIST69 said:

First of all...



Yeah right =P


Nvidia recommends 26-28 amps for 7900gs sli. You've got 34, so it will definitely work, just a question of how long. It might overheat like others said, so maybe you could put a fan on it. Or you could get a dedicated video card power supply (like this http://www.hardwarehounds.com/techspotlight/powerexpress.shtml) as a cheaper way of upgrading the psu.

I like your water cooling setup btw.

Click to expand...

btw your 144W was off... had you shown me the right spec I would've said it works .

Yes it can work. YOU are wrong. What nvidia reccomends is the amperage draw for the whole system. If you have 2 130W 7950gx2's and 1 65W cpu 1 hard drive and 2x1gb ram you may draw 325W off the 12rail and then maybe a few amps on the other rails. You can run it off the 12v rail if the psu has enough power on the 12v rail.

Wattage doesn't matter and Nvidia's and ATI's specs are only for safe measure. If the only listed that most people would need 25 amps then people would only buy that amount of power and then complain when it didn't work.

The fan on the power supply is working wonders, it never gets hot. I read a review of the Phantom 500w which basically said that it's a 350w Phantom with a fan where I have mine. I guess i've just made one!

Okay, well CS:Source seems to be fine for the 10 minutes I played it. I will play a game for longer, just don't have the time at the minute, and 3dmark 05 is taking an eternity to download.

Far Cry however, is having some difficulty:



The water is showing up as you can see, yet the game runs flawlessly smooth. Everything is set to the max, either Very High or Ultra High and the frame rates are fantastic, but the water is still messed up.

It looks like the cards are artifacting, but my watercooling is rigged up to 2 radiators outside the house and one card is sitting at 24*C whilst the other is 15*C, so no problems with the temperatures.

Could it be the power?

could be... I guess... lol

Assuming it's not a software issue, that kind of artifacting looks more like a memory issue imo. What kind of cooling do you have on the video card memory chips?

Dude, please buy a quality 600 or 700 watt powersupply. I would truly hate to hear that any more of your components went "Pop".

Check these PSU Calculators
http://www.zippy.com.tw/P_Budget.asp?lv_rfnbr=2
http://extreme.outervision.com/index.jsp - Not sure I trust this one. Reccommendations seem low.

Good luck.