GTX 285 tri-SLI, 850w psu? - Page 3 - Overclock.net

Slightly skewed · 07-02-09

Quote:

Originally Posted by bumsoil

jonnyGURU did tri-sli gtx 280's with a BFG 800, so i think you will be fine.

http://www.jonnyguru.com/forums/show...light=adapters

Ok, but it looks like a stock CPU setting with a stock cooler, so add a few more watts for the OP's OC. And are those card OC'd?

seward · 07-02-09

I should say that not only did I not realize that my psu only had 4 6-pin connectors, I also didn't realize that my cards each came with 2 molex/6-pin adapters (2xmolex->1x6pin)

. So I guess I can do this, as long as I feel comfortable with using those adapters, and that wattage...I'm pretty sure I've still got a few unused molex plugs on that psu. We'll see. I'll certainly put some benches up if I do it. Uh anyone with any experience using those adapters?

seward · 07-03-09

Quote:

Originally Posted by bumsoil

jonnyGURU did tri-sli gtx 280's with a BFG 800, so i think you will be fine.

http://www.jonnyguru.com/forums/show...light=adapters

I'd like to know what his cpu/gpu clocks were. Interesting.

edit: stock e6750...say, ~130w at load? Hm...I think my psu is better...

Slightly skewed · 07-03-09

Quote:

Originally Posted by seward

I should say that not only did I not realize that my psu only had 4 6-pin connectors, I also didn't realize that my cards each came with 2 molex/6-pin adapters (2xmolex->1x6pin)

. So I guess I can do this, as long as I feel comfortable with using those adapters, and that wattage...I'm pretty sure I've still got a few unused molex plugs on that psu. We'll see. I'll certainly put some benches up if I do it. Uh anyone with any experience using those adapters?

There not really reccomended, but you can use them. Make sure that you don't overload anyone rail, if you know what I mean.

seward · 07-04-09

Not sure if I'll have the time or inclination to deal with setting up 3 cards, but here's a pretty interesting article about tri-SLI GTX 285s, with some good power stuff:

http://www.tweaktown.com/articles/17...d/index11.html

I've found some things here and elsewhere that indicate that Crysis scales well (~2.5x1 card) in tri-SLI. Does ok in SLI too...

Not sure if it's worth switching to onboard audio...it would certainly push my psu to its limits.

brettjv · 07-04-09

I just got done running a whole slew of benches running quad-sli (2x295) on my Coolermaster Real Power 850W w/my OC'd i7 ... not a hiccup. But this PSU has 2x8pin and 2x6pin, with a dedicated 26A rail to each 8pin, and a dedicated 18A rail to each 6pin. Total 12V is 64A on this PSU.

I bet your 850 will handle it fine with the proper adapters, myself. Maybe it's not totally optimal, but ...

Zap · 07-04-09

Quote:

Originally Posted by seward

I'd like to know what his cpu/gpu clocks were. Interesting.

edit: stock e6750...say, ~130w at load? Hm...I think my psu is better...

It was my test rig at work.

jonnyGURU just took and posted the pics.

The E6750 was at stock speed and I think those 65nm Conroe chips were 65W. I think the cards were stock speed as well.

The three GTX 285 on a Corsair 850W may have better success even though the overclocked Q9650 draws a lot more power. The reason is that the GTX 285 uses less power, plus the extra 50W of the Corsair is probably all on the +12v.

That being said, while the three GTX 280 ran on that setup using an 800W PSU, it wasn't what I would consider completely stable. The Kill-A-Watt is too slow to measure the transient spikes in power draw that happens on occasion, plus the system was only running the CPU fan and one HDD. Sometimes it would run a 3DMark loop just fine and other times the system would just turn off from the power supply OCP (over current protection) tripping. While we were mighty impressed and entertained (as I'm sure all geeky computer enthusiasts can be at times) I would not run such a setup and expect complete long-term stability.

The other thing is that even if a PSU can put out that power just fine, it is extremely rough on it to put out near 100% long term. For instance HardOCP's PSU review methodology includes a torture test by running the PSU in a controlled environment for 8 hours at 80% output. If several hours at only 80% output is considered a torture test, imagine what you'd be doing to that poor Corsair 850W. Note that yes, there are PSUs that will pass 100% load, but fail 8 hours worth of 80% load.

seward · 07-05-09

Quote:

Originally Posted by Zap

It was my test rig at work.

jonnyGURU just took and posted the pics.

The E6750 was at stock speed and I think those 65nm Conroe chips were 65W. I think the cards were stock speed as well.

The three GTX 285 on a Corsair 850W may have better success even though the overclocked Q9650 draws a lot more power. The reason is that the GTX 285 uses less power, plus the extra 50W of the Corsair is probably all on the +12v.

That being said, while the three GTX 280 ran on that setup using an 800W PSU, it wasn't what I would consider completely stable. The Kill-A-Watt is too slow to measure the transient spikes in power draw that happens on occasion, plus the system was only running the CPU fan and one HDD. Sometimes it would run a 3DMark loop just fine and other times the system would just turn off from the power supply OCP (over current protection) tripping. While we were mighty impressed and entertained (as I'm sure all geeky computer enthusiasts can be at times) I would not run such a setup and expect complete long-term stability.

The other thing is that even if a PSU can put out that power just fine, it is extremely rough on it to put out near 100% long term. For instance HardOCP's PSU review methodology includes a torture test by running the PSU in a controlled environment for 8 hours at 80% output. If several hours at only 80% output is considered a torture test, imagine what you'd be doing to that poor Corsair 850W. Note that yes, there are PSUs that will pass 100% load, but fail 8 hours worth of 80% load.

Hey man, thanks for reply...yeah, I'm somewhat put off by the risk, plus the hassle (e.g. using onboard audio). I'd like to get a few hours worth of play along with benches. It looks like the card does scale well in tri-SLI, at least relative to other games. Of course, it scales pretty well in regular SLI too...

Slightly skewed · 07-05-09

Quote:

Originally Posted by seward

Hey man, thanks for reply...yeah, I'm somewhat put off by the risk, plus the hassle (e.g. using onboard audio). I'd like to get a few hours worth of play along with benches. It looks like the card does scale well in tri-SLI, at least relative to other games. Of course, it scales pretty well in regular SLI too...

Ya don't let the naysayers discourage you from SLI/TRI SLI. For most (current) games it's not effective. But, some of the most demanding games, and benchmarks (current) and future will benfit and take advantage of multi gpu set-ups.

Sell the one you have, or return is and get a ~1000W unit and there will be no more power worries.

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GTX 285 tri-SLI, 850w psu?

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