silverstone 650w and sli 7900 GTX's

[panthony12]

hi, wondering if someone can just give me a straight answer on this! I have the 650w silverstone zeus and want to buy two evga 7900 GTX's for my setup. Will this psu be able to power them with good stability? I just bought the psu not too long ago, and would hate to have to buy another one so fast. My setup:

AMD X2 4400+ OC'ed to 2.6 ghz
2 GB OCZ Platinum DDR400 (PC3200)
2 SATA WD 150GB HDD's 10,000 RPM
ASUS A8N-SLI MB
Soundblaster Platinum 5.1
2 EVGA 7900 GTX SLI
2 DVD Burner's
Zalman Reserator 2 w/Kosaah SLI Waterblocks

Please help me avoid buying another PSU.
It seems like i am having to constantly do this!
PSU's suck

Thanks for any help u have!

 

[tool_462]

If I am not mistaken, the Zeus has Quad 12v rails? Averaging 15A each. So yes, your PSU will handle the 7900GTX's fine.

 

[phreejak]

Those 7900 GTX, at best, will consume about 200 - 210 watts of your PSU (a little more if you overclock). The rest of your equipment isn't as demanding so that PSU will do fine. I don't think that your equipment will over draw on the amps (+12V1@13A, +12V2@18A, +12V3@16A, +12V4@8A ) so it looks like you're ok.

 

[panthony12]

THANKS FOR YOUR HELP GUYS, THOSE ARE SOME REFRESHING WORDS READ. But, maybe u can help me with this question too. How do i distribute what peice of hardware goes on what 12V rail?

For example: i want to put one of my cpu cores on the 12V1, and the other on 12V2. Then i want to put one VGA card on 12V3, and the other on 12V4 etc etc...

Is it automatically done or what? Don't know much about the psu and how to fool with it! Would appreciate any advice possible. Thanks

 

[phreejak]

The PSU handles that.

 

[AceCobra1]

If I am not mistaken, the Zeus has Quad 12v rails? Averaging 15A each. So yes, your PSU will handle the 7900GTX's fine.

Can I ask... I have SLI 7900 GTXs setup

I purchased and ran the CoolerMaster iGreen 600W PSU yesterday...

It freezes windows when I try to run anything like 3D mark... sometimes it just restarts randomyly... I've not even played any games yet!

Should that PSU handle 2 x GTXs ?

My setup is

Pentium D 805
1GB XMS ram
2 DVDRW
1 HDD
etc...

no much power consumed at all! Please help

 

[Aids]

If the rails on that PSU are over 32 combined, then it should be ok. What are the 12v Rails?

 

[AceCobra1]

If the rails on that PSU are over 32 combined, then it should be ok. What are the 12v Rails?

Yeah... but that is the peak... apprently the average is 16A and 14A each... so does that mean if I run a single card, it will be less stable since I am using 1 rail which only gives out 16A when it really recommended 22A?

 

[Dahak]

Indeed it will.I run two 7800gt in sli mode and my psu is only 520watt.I believe my 7800gt's are also more power hungry than the 7900gtx'sso ya no worries,enjoy your gaming experience.

Dahak

EVGA NF4 SLI MB
X2 4400+@2.4 S-939
2 7800GT'S IN SLI MODE
2X1GIG DDR400 MEMORY IN DC MODE
WD300GIG HD
520WATT PSU
EXTREME 19IN.MONITOR

 

[darkstar782]

Is that D805 overclocked? The 805 eats wattage when overclocked.

 

[AceCobra1]

No....

My harddiscs are beggin just to get reformated... I'm just backin up some stuff...

I'll update again!.... Just got about 100GB to backup lol

Can u guys say for definate that this PSU is OK ?

 

[tool_462]

Is that D805 overclocked? The 805 eats wattage when overclocked.

This is true. Also, you may want to check your PSU's manual, I have seen a few multi-railed PSU's that have certain leads that are powered by certain rails. If it is an SLI ready PSU and you aren't using adapters, just check and see if you can put all your other hardware on one rail and the PCIe plugs shouldn't be maxing out on amperage I wouldn't think.

 

[wolfman140]

Someone explain to me what the devil dual 12v rails means? I'm assuming dual rails is a plus, but what does that do for you technically?

 

[phreejak]

older (and even a slight few newer ones) usually had a single 12v rail. This was used to feed power to the various components of the motherboard. What you will see is that, to prevent the rails from buring out, they began creating multiple railed PSU - dual, triple, quad and now, five). The norm, today, seems to be the quad 12v rails. Though, this is typically found on PSUs around 600 watts or greater.

In a quad 12v rail system the first rail (referenced as 12V 1 from this point on), feeds the motherboard via the 20/24-pin ATX connector. The second rail (12V 2 ) also feeds the motherboard but this time via the 4/8-pin 12V connectors. The third rail (12V 3 ) feeds the PCI-Express cards via the two PEG (PCI Express Graphics) connectors. The final rail (12V 4 ) feeds the molex, floppy, and SATA connectors.

 

[tool_462]

Just a quick question for you Phreejak. I remember reading something (months ago, cant find it on google) that for an overclocking system it would be advantageous to use a high amperage single rail PSU than a split rail lower amps per rail PSU. Any truth to that? I can't see a reason why, since most big name PSU producers are only coming out with multi-rail products as of late.

 

[AceCobra1]

The PSU will be more then enough. You will have 42A combined on the +12v rails.
Looking at the PSU you will have these amps on the +12v Rails.
13A
18A
16A
8A
With a max output of 504W on the +12v rails. Giving you a total of 42A.

This is what I've got:

http://www.pcper.com/article.php?aid=257

So the bottom line is that that PSU will be definately more than enough to power both my cards? Will it be more stable with 1 or 2 cards together since if I connect both 12V connectors, I'll have 30A in total while if I connect only one 12v connector, i'll end up with 16A when it said it would be preffered if I have 22A ? The asus box said if I had 2 cards, ideally, you'd want 30A so if I use both connectors I'd be connecting 16A + 14A = 30A ? Am I right ? If I connect 1 connector, I take it that the other 14A from the other connector is made redundant ?

 

[phreejak]

Well, I am not going to say that I am any kind of an expert on PSUs - my thing is water/TEC cooling (I'd defer to this type of issue to people like mpilchfamily above).

But, in these forums I've seen arguments for both multiple rail and single rail PSUs. Since I have to deal, somewhat, with PSUs because of their relative necessity to what I focus on I've found that parties for both sides will kick and scream for their side of things - they'll point out certain reviews, cite statistics, you get the picture. I do know this, though: An industry will flow with whatever is going to be more popular nd advantageous when dealing with any kind of product. I think that is why you are seeing PSU with multiple rails and active PFC more now. I, for one, like the idea of multiple rails as this prevents overdraw from any one single rail and is better suited against potential breakdown. With multiple rails, when one is dedicated to, say, graphics, you know that is going to be the only draw on it - with the other rails being dedicated to the various other components. To mind, I can only think of one company right now (I am just not trying too had to remember though - heh) that produces a single railed state of the art PSU - Athena.

I think there is a reason that the major players all are producing multiple railed PSUs. I just like having the peace of mind of dedicated rails for specific components being just that - dedicated and seperate.

 

[phreejak]

wow, you're making my head spin - it's only lunch time and I'm having to try and figure out math. Usually, I have a specific rule that says no mather until at least 3 in the afternoon.

Bottom line, you are going to be fine with that PSU and the amperage.

 

[AceCobra1]

Thanks for both your inputs... much appreciated Learn something new everyday!

 

[tool_462]

Thanks for the explanation. I also think that companies may lean towards "Dual Rail" "Quad Rail" designs because it simply sounds cool. Whether or not there is a performance gain, people will think "double = double performance" and they will sell (potentially and theoretically) more product.