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SLI Power consumption

X

xyber

Limp Gawd
Joined
Aug 8, 2004
Messages
156
dual 6800U with each of them needing at least a 480W PSU. Any solutions? Two PSUs in a large case like the Cooler Master CM Stacker?
 
A GF6800U dosn't "need at least a 480 watt"...
In fact they only use 9 watts more than a X800XT-PE...

Terra - Some myths die hard...
 
I picked up a coolermaster stacker for that exact reason, dual 550 watt PSU. I think 1100 watts will handle 2 6800 ultras just fine.
 
would something like the OCZ powerstream 520W do fine for dual 6800GT?
 
xyber said:
would something like the OCZ powerstream 520W do fine for dual 6800GT?
Click to expand...

Nvidia recommends a 300 watt PSU for a system with 1 GF6800GT.
Add the power comsumption of appr. 80 watt for 1 more GF6800GT, and you end up with demand off 380 watt in total
But my guess is that a good quality 350 watt PSU would be sufficient...

Terra...

Edit: I misunderstood your question and did the math for 2 GF6800U's.
 
bvincent said:
I picked up a coolermaster stacker for that exact reason, dual 550 watt PSU. I think 1100 watts will handle 2 6800 ultras just fine.
Click to expand...

Talk about overkill ;)
Nvidia recommends a 350 watt PSU for system with 1 GF6800U
Add the appr. 80 watt for 1 more GF6800U and you end up with a demand of 430 watt in total.
But a good quality 450 PSU should be just fine :)

Terra...
 
That 480W is for the ENTIRE system, not video card alone, and many have even shown that as being a huge overestimate (which is why nvidia knocked it down to 350W). A 480W should be able to handle SLI alone.
 
But when you OC both the GPUs, your ram and CPU, the need of power will be much higher
 
Terra said:
Talk about overkill ;)
Nvidia recommends a 350 watt PSU for system with 1 GF6800U
Add the appr. 80 watt for 1 more GF6800U and you end up with a demand of 430 watt in total.
But a good quality 450 PSU should be just fine :)

Terra...
Click to expand...

Definately overkill but I got other uses in mind for all that power, it'll also be running my watercooling setup as well.

A Thermaltake 480 watt psu (not what I consider quality anymore) did not cut it for me with even one 6800u. Along with my oc'd prescott, 4 hard drives, cathode tubes and half dozen fans it was not supplying enough on the +12 volt rail to keep everything stable. I vowed to never be deficient in the power department again, hence the overkill :)
 
bvincent said:
I picked up a coolermaster stacker for that exact reason, dual 550 watt PSU. I think 1100 watts will handle 2 6800 ultras just fine.
Click to expand...

do the lights flicker when you turn on your computer????

you dont have enough power for SLI unless you knock out a city grid and start an electrical fire just by turning your computer on....
 
xSyzygy666x said:
do the lights flicker when you turn on your computer????

you dont have enough power for SLI unless you knock out a city grid and start an electrical fire just by turning your computer on....
Click to expand...


ROFL sig worthy right there. classic...

anyway, i dunno how much power an SLI system is going to require. not to sound like a whore or troll or anything but notice nV is quick to post super uber omg frame rates etc of such setups but(to my knowledege anyway) have yet to announce power requirements of the said setup. its definitely not gonna be easy on the wallet either way thats for sure.
 
dual x-connects or dual antec neo's in a CM stacker would pwn face, if i had enough for SLI, thats exactly what id get.
 
why don't you take two Antec 550w truepower PSUs and link them together plug one into each video card power power connector link the green wires from the PSU together and they should begin to act as one and give you all the power you need. It may be a little uneconomical however, it will give you all the power you will ever need.
 
Do you guys think that antec TP430 will be enought for 2 6600GT cards?
It should be 100W for 90 amd CPU (porbably more like 80-90), 30 for mobo and memory, 125 W for 3 hardrives and 2 optical drives and around 120-140 W for two 6600GT's. So that's 390 W in worst case.
 
Depends on the quality of the powersupply. Also, "end" wattage usage is not the same as overall rated wattage usage.

IE: The *new* ATX with 24-pin motherboard connector supplies should be more reliable than the old 20-pin. Even though both might be rated at say 500 watts, the new one is probably more futureproof because of it. Its one of the reasons Intel used 775 pins instead of 478, more stable voltage over a greater number of pins (both voltage active, and grounds)

It also comes down to wiring guages, look for the thickest cables you can find, so that it can pump the maximum amount of amperage to your peripherals without losing energy due to heat.

http://www.pcguide.com/ref/power/sup/partsMotherboard-c.html Is a good but old guide on the power connectors.

And most powersupplies run at approx 60 percent energy conversion efficiency, not counting loss due to thin wiring and high loads, or additional losses due to 12V to CPU voltage (typically around 1.5Volts) conversions. So yes, this all has to be factored in.
 
Michaelius said:
and around 120-140 W for two 6600GT's.
Click to expand...
A 6600GT consumes around 48 watts under load so that's 100W for the pair. 125W for the drives may be a bit high too - a new Maxtor 7200rpm SATA 8MB drives uses around 12.2W under load (seek) so that's 36.6W for the HDDs. Add in say 30W each for the DVD-writers and that's 60 + 36.6 = 96.6W for all your drives. Realistically you'll never be putting them all under maximum load simultaneously either.

But when it comes to working out how 'big' a PSU you need I'd rather use your figures than mine. ;)
 
Please note that the specs given for consumption given on the parts is "end" usage.

Take for example a P4 that is "rated" to use 103 watts. At the pinout of the 478/775 connector, yes it is using 103 watts there. But at the 12Volt CPU connector it may be drawing closer to 140watts at that point.

The processor asks for 103 watts at say 1.4 volts, the capacitors lose a small amount of energy smoothing the dips and valleys in power fluctuations, the mosfets (some now needing heatsinks to cool) conversion can be very inefficient. By the time you calculate the 12V motherboard power connector to the pinout of the CPU, it can be quite hefty. Now, if you are going to factor that into the mobo consumption along with the other things like the northbridge, thats fine but a lot of people just seem to ignore it. This is not even mentioning the approximate 60 percent power conversion inefficiency from 120volt to 12, 5, and 3.3 volt of most powersupplies (the best powersupplies are 80 percent)
 
fallguy said:
This one shows the 6800U at 77-123w.
Click to expand...
The 6800U draws around 93% of it's power from the extra molex connectors and only takes 4.76W from the AGP slot. The 123W number assumes the 6800U takes the maximum 46W from the AGP slot and is therefore completely wrong.
 
anyone have an idea on the most probable average price for the SLI nforce4 moboards will be? Also, for SLI, can you for example buy one 6600GT PCIE one time and when u have enough, get another one and add it on? Or do you have to buy some 'special' linked PCIE cards? Just wondering, because im planning to get into dual GPUs when they come into the market
 
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