Im confused? SLI & CrossFire

FairDoos

FairDoos

Active Member
Ok so recently ive bought a new PSU as my old one didnt power everything :l Owell but yer to the point.. My new PSU says its SLI Certified right but i was thinking generally GFX Cards have 2 power slots like 6-pins and there is only 2 on the PSU so if one card is using the 2 already on the PSU where is the other card going to get its power from?

Sorry if this is obvious im a noob to SLI & CrossFire :o
 
If you had 2x 9600GTs' (or any graphics card that uses one 6pin connector) and a compatible motherboard it could do sli. Same goes for crossfire.
 
linkin93 said:
If you had 2x 9600GTs' (or any graphics card that uses one 6pin connector) and a compatible motherboard it could do sli. Same goes for crossfire.
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What about say if i wanted 2 4890's in CrossFire how would you go about doing that?
 
FairDoos said:
I have a 700W ModXStream PRO do you think that could handle 2 4890s?
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Should be alright. I had the 600 watt model, solid PSU. You should have enough connectors. I don't know why but I never liked the thought of using 6 pin to molex adapters.
 
Ethan3.14159 said:
Should be alright. I had the 600 watt model, solid PSU. You should have enough connectors. I don't know why but I never liked the thought of using 6 pin to molex adapters.
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Im completely the same im still sceptical of it. Is there any other PSU that supplys like another 2 ports for Crossfire?
 
Bodaggit23 said:
I don't think so.

The 700W ModXStream Pro only has 552watts on the 12+ rail.

ATI recommends at least 600watts for Crossfire.
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You do realize that ATi implied 600 watts for the entire system? 2 4890's will not draw anywhere close to 552 watts at full load nor use all of the amps. They do have a max power draw, which is about 150 watts per 4890.

Yes, FairDoos, what you have will be fine for 2 4890's. I would run 2 4890's on the 650 watt Silverstone I have right now without a 2nd thought.
 
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Ethan3.14159 said:
You do realize that ATi implied 600 watts for the entire system? 2 4890's will not draw anywhere close to 552 watts at full load nor use all of the amps. They do have a max power draw, which is about 150 watts per 4890.

Yes, FairDoos, what you have will be fine for 2 4890's. I would run 2 4890's on the 650 watt Silverstone I have right now without a 2nd thought.
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Ok now im scared i dont know who to go with :'( :gun:
 
If you want to upgrade your PSU that's fine. Certainly won't hurt. I'm just saying that it isn't necessary for what you want.
 
Ethan3.14159 said:
If you want to upgrade your PSU that's fine. Certainly won't hurt. I'm just saying that it isn't necessary for what you want.
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What about if i wanted 2 5850's in Crossfire? ;)

Which i probably will get in the future if i can get to understand Crossfire :)
 
As you can see here the 5850 uses slightly less power than the 4890. Notice the full system load of the 2 5850's in crossfire? 469 watts. You'll be fine. Also, a worthy note that it uses 70 watts less than the GTX 285, which the 5850 beats.
 
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Bodaggit23 said:
Of course, but they recommend that number for a reason.

So even if the OCZ 750 will run those two cards, there's still the issue of the lack of power connectors.

@FairDoos
That's a nice power supply and it would
definitely work.
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The number recommended is a safe estimate for those who have off brand 800 watt PSU's. There is no "if" about if it will run it or not. Just use the molex connectors that come with each card. They still run off the 12v rail.

I'm not into recommending wasting money.

Look at the total system power consumption:
Power%20Consumption.png


A new PSU isn't necessary.
 
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I think you've taken this as an argument, and it's simply not the case.

He asked if it will work, and I said I don't think so based on ATI's recommended
specs.

You think it will. Fair enough.

If it were me, I would probably try it first before purchasing a new psu.

On a side note, how can OCZ advertise that PSU @700watts, since it only
has 552watts?
 
Bodaggit23 said:
I think you've taken this as an argument, and it's simply not the case.

He asked if it will work, and I said I don't think so based on ATI's recommended
specs.

You think it will. Fair enough.

If it were me, I would probably try it first before purchasing a new psu.

On a side note, how can OCZ advertise that PSU @700watts, since it only
has 552watts?
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Fair enough. Didn't mean to make it come off as an argument. :)

552 on the 12v rails. There are the other rails too.
17-341-018-07.jpg
 
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