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ZACHOW3

Dual 7900gtx Cards

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Im running my old OCZ 520W powerstream and it works fine with 2 7900 gtx's and my x2-4800 and 1 hd and 1 plextor dvd burner. I dont know if it's enough. I think it is, just barely. I had a brand new Enermax 620 Liberty and I think it was blowing up my evga cards. I'm on my third set and they are fine with the OCZ psu. The Enermax is going back to Newegg. Anyone have any brilliant ideas about a PSU?? I saw a Kilowatt one the other day on Newegg.....It was rated for quad SLI....Is it really necessary?

 

--EJM

 

BTW...I love my 7900's....8500 in 3dmark 06 @ stock...not bad....13500 in 05....It'll do.

 

 

Now that's pushing it. How long have you had this setup? So you haven't noticed any issue with a 28amp PSU running a dual core with memory overclocked with 2x7900GTX's?

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Anyone running 2 of these cards in SLI? Mine are XFX not that that really matters but with my OCZ Powerstream 600 and an FX-57 I think I might be pushing the envelope with this PS. And I thought that my $$$ PS would allow me room for future upgrading but these 7900GTX cards are power hungry monsters. Runs great with one card but two might be pushing it. I have to much invested (ask my wife) to buy another PS but if thats what it takes to run this combination than I will(of course the little misses wont know). Any thoughts on if I should be okay with what i have or recommendations on a PS that will work for my setup?

 

7900's are a long way from power hungry monsters even when fully modded and running well over 800mhz core. It is the x1900's that need to be sold with an optional nuclear generator to power them.

 

Viper

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7900's are a long way from power hungry monsters even when fully modded and running well over 800mhz core. It is the x1900's that need to be sold with an optional nuclear generator to power them.

 

Viper

 

 

I wanted to go with ATI for a change, but they require too much power for my setup.

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It sounds like I have the power to run dual 7900GTX's. Had a problem though where I uninstalled the drivers to my single card and then installed my second card and reinstalled the drivers.(From a tip I received) But then it wouldnt boot!! After tearing my hair out I decided to start from scratch.Did a clean reinstall of XP and it worked. Well almost. The Nvidia window says im running multi GPU"s. But the computer is very sluggish. Much slower then a single card. Just wondering, Do I need to Install the drivers for each individual card. Am I missing something obvious? Been away for a few days and havent been able to play with it.I think i'm close but obviously missing something.

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Nice rig there :)

 

From what I have seen, the OCZ 600 will not run the High-end SLi GPUs esp these new ones. Some other members have had this PSU with the 78GTX512 and had to change out to a higher rating PSU or with one that has better load spread across the Rails. They too were experinecing odd shut-downs, a slow system or poor 3D benchmarks.

 

The 79GTX draw approx 8-9A each and the PSU has only two +12v rails providing up around 36A, so this alone will take out one rail and you have other kit and the MB etc to contend with.

 

The PCIe supply rails have no gudiance in the ATX12V specifications so it is up to the manufacturers to deal with it. They are now starting to realise this hence you see the newer PSUs have better load balancing or are more informative about how to balance these GPUs across all of the available rails.

 

Have a look at one of these as they have been rated to cover your GPUs

 

FSP Group EPSILON FX600-GLN 600W

 

FSP Group EPSILON FX700-GLN 700W

 

PC Power & Cooling Turbo-Cool 1KW (TC1KW)

 

PC Power & Cooling Turbo-Cool 1KW-Quad SLI (TC1KW4E)

 

PC Power & Cooling Turbo-Cool® 850 SLI (850ETX-PFC)

 

Silverstone ST56ZF 560W

 

Sparkle Power FSP600-80GLC

 

Sparkle Power FSP650-80GLC

 

Sparkle Power FSP550PLG-SLI 550W

 

Tagan TG900-U95 (TURBOJET) 900W

 

GL

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I'm hearing conflicting responses about whether or not my PSU will handle 79000gtx cards in SLI. I callled PC Power and cooling but as of this post wasnt able to reach anyone but left a voicemail. Was thinking th PC Power @ Cooling Turbo cool 850 SLI should do the trick since this was a recommended PSU on a previous post but it's $450.00 on Newegg. I realy dont want to have to spend that kind of money but I would like to run in SLI. I'm confused. Both cards are running SLI right now but the graphics are very sluggish which suggests to me that Is a PSU problem. That my system is under powered. Any thoughts?

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I'm hearing conflicting responses about whether or not my PSU will handle 79000gtx cards in SLI. I callled PC Power and cooling but as of this post wasnt able to reach anyone but left a voicemail. Was thinking th PC Power @ Cooling Turbo cool 850 SLI should do the trick since this was a recommended PSU on a previous post but it's $450.00 on Newegg. I realy dont want to have to spend that kind of money but I would like to run in SLI. I'm confused. Both cards are running SLI right now but the graphics are very sluggish which suggests to me that Is a PSU problem. That my system is under powered. Any thoughts?

 

Probably not nor will any ATX 2.0/2.1 with a 12V1/12V2 split, that follows the letter of the ATX 2.0/2.1 spec. do so reliably. It has nothing to do with the total wattage or the total current the PS can supply at 12 volts but on a bad spec from Intel that came out long before SLI and CrossFire was a reality. BTW Intel has silently dropped the requirement of a PS being ATX 2.0/2.1 to get the Intel approved logo).

 

The max over current limit on either 12V1/12V2 of a compliant ATX 2.0/2.1 PS is 20amps. 12V1 powers the ATX connector (often referred to as CPU1), all the molex and SATA connectors, and the PCIe aux connectors. 12V2 only powers the 4/6/8 pin motherboard aux connector (sometimes referred to CPU2) and nothing else.

 

What is happening is when the SLI pair loads up in 3D (the CPU also loads up then as well) the current bring drawn by the CPU1, your drives, fans and the cards is pushing over 20 amps on 12V1 and the PS is going into current limit on the 12V rail.

 

An OCZ PowerStream 520w with a single 33A 12V rail has no problem but it is not ATX 2.0/2.1 compliant. There are many PS's out now with three 12V rails where 12V3 runs the PCIe aux connectors. There are other flavors as well. As least one ATX 2.0/2.1 compliant PS (I think it is Tagen) has a switch that will bridge the 12V1 and 12V2 rails together (it is no longer ATX 2.0/2.1 compliant like that) giving you an effective single 12V rail PS with large current capacity.

 

The PC Power and cooling 850 and 1000 watts supplies have 12V1/12V2 compliant with the ATX 2.0/2.1 spec and then use a monster current 12V3 rail (which powers the PCIe aux connectors), drives, molex, etc. The spec doesn't expressly cover the third rail but technically the PS is not ATX 2.0/2.1 compliant nor does it comply with UL on the 3rd 12V rail (where no rail can have a current limit higher than 240 volt/amps (that is 12 volts at 20 amps).

 

In some ways consider yourself lucky as a single modded x1900XT running 800+ core with increased Vcore can sometimes trip up a ATX 2.0/2.1 compliant PS. A pair of 7800-512's would always take an ATX 2.0/2.1 compliant PS down.

 

When Intel dreamed up the split 12V rail PS spec PS makers universally shivered and knew it would be a migraine waiting for a place to strike but there was nothing they could do about it nor was there a need to at that precise moment it time. That time came with the advent of 7800-512, 7900's and x1900's in SLI and CrossFire configurations.

 

Viper

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So forgive me if im wrong but if I understand correctly I shouldnt have gone with a PSU with split 12V rails. What specific PSU would power my system. Ive seen the list provided earllier in this thread and guess I didnt do my research very well as I havent even heard of many of these PSU brands before. Am I than looking for a good single 12V rail PSU to power everything. Still somewhat confused.

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Well, I guess I'm screwed too. I'm just thinking about the Pc power and cooling 1000W. I dont care about the money. All I want to know is if it will work properly. Im down to 1 7900 gtx right now because the Enermax 620Wcouldnt hang and my OCZ 520 certainly cannot hang with my setup.

 

Will the 1KW Pc Power and Cooling PSU Power My setup Below?

 

Thanks Guys.

 

--EJM

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