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How to connect sli-ready PSU (Corsair TX650W) to sli GTX 460?

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August 4, 2010 4:03:09 AM

The power supply (Corsair TX650W) only comes with two 6+2 PCI-Express connectors; my question is that, since each GTX 460 card needs two six pin connectors as a power supply, how do I provide sufficient power? The PSU says that it is SLI-ready.

Edit- I forgot to mention that I have an additional 4-pin molex cable and what seem to be molex adapters for the video card.

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a b B Homebuilt system
a c 83 ) Power supply
August 4, 2010 5:03:13 AM

You'll need to get 4pin molex to 6pin PCIe adapters. Make sure the 650W has enough amps for both of the GTS460s. I think you'll be ok but I'm not sure.
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August 4, 2010 5:12:55 AM

Thanks for the help! Is it ok to use 6+2 cables (only using the six) for one card and the adapters for the other?
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a b B Homebuilt system
a c 83 ) Power supply
August 4, 2010 6:13:39 AM

Won't matter. Corsair uses a single 12V rail so they all come from the same source.
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August 4, 2010 6:26:07 AM

On my first attempt to turn on the PC I got the green standby light and a red 'VGA error' led (edit-it is a quick red flash), and I think this prevented the rest of the PC from turning on at all. I thought I might have done something wrong! I will read the troubleshooting thread, but I have a feeling it has to do with the PSU connectors.
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a b B Homebuilt system
a c 83 ) Power supply
August 4, 2010 7:23:20 AM

Everything plugged in tight? Both cards had two power plugs?
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August 4, 2010 8:08:04 AM

All of the cables seem plugged in tight, and both cards have two plugs.

Like I said, on one card I am using a 6+2 PCI-Express cable (without the +2), and on the other I am using molex adapters which came with the GPUs (the molex cable has an unused MOBO connector by the way- could this be the problem?)

Could the problem be something beside the GPUs? I read elsewhere that during POST each of the leds should blink. The only things that turned on were the green standby power light and a brief red flash from the VGA led.

EDIT- When I say nothing else turns on, I mean nothing on the monitor, no fans, and no other lights. I should receive my internal pc speaker in the mail later, so I can use the beep codes if necessary. If there is something wrong with the VGA, could it affect the rest of the POST?

Thanks for trying to help me troubleshoot by the way. I certainly need it since I am a first time system builder.
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a b B Homebuilt system
a c 83 ) Power supply
August 4, 2010 9:52:09 AM

Yes. BOTH molex plugs need to have something plugged into them. Preferably from different "strands". (so that to much current doesn't go throw one set of wires.) You might need to do some rewiring to make this work.
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a b ) Power supply
August 4, 2010 6:33:22 PM

Did you plug in the EPS 12v connector to the motherboard
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August 4, 2010 7:00:10 PM

The 8-pin power cable? Yes, it is plugged in, though it was very hard to do since my HSF (the scythe mugen 2) is so large. Really I should have done it before HSF installation, but I had no prior experience with system building. I did, however, make sure that it was plugged in securely by using a screw driver to push down on it.

Here are my system specs for future reference by the way:

CPU- Intel Core i5-750 Lynnfield 2.66GHz LGA 1156 95W Quad-Core Processor BX80605I5750

MOBO- ASUS P7P55D-E Pro LGA 1156 Intel P55 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

RAM- G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL7D-4GBRM

HDD- SAMSUNG Spinpoint F3 HD103SJ 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive

GPU- [SLI] EVGA 768-P3-1362-TR GeForce GTX 460 (Fermi) Superclocked 768MB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

PSU- CORSAIR CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply

CASE- Antec Three Hundred Illusion Black Steel ATX Mid Tower Computer Case

HSF- Scythe SCMG-2100 Sleeve CPU Cooler

Thermal Paste- ARCTIC COOLING MX-2 Thermal Compound

ODD- Sony Optiarc CD/DVD Burner Black SATA Model AD-7260S-0B - OEM
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a b ) Power supply
August 4, 2010 8:29:01 PM

does it post with one card?
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August 5, 2010 12:46:07 AM

I will try posting it with one card later, and I will tell you how it works.

But I think a more basic problem is that I put my PSU in wrong! It is on the bottom of the case but the fan vent is not facing the top. Could this be the problem?
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a b B Homebuilt system
a c 83 ) Power supply
August 5, 2010 12:50:39 AM

I don't see how. I get the feeling its an issue with your adapters. No motherboard plug should be on the same chain.
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August 5, 2010 12:56:38 AM

Are you saying that a MOBO connector should not be found on my 4 pin molex cables? (I have one on both my molex cables).

I will try to upload some pictures later to show you guys the situation.
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a b ) Power supply
August 5, 2010 1:03:43 AM

kerryking said:
I will try posting it with one card later, and I will tell you how it works.

But I think a more basic problem is that I put my PSU in wrong! It is on the bottom of the case but the fan vent is not facing the top. Could this be the problem?


my PSU fan also was facing the top of the case, it wont make a difference as it will suck the hot air from the top of the case out through the back. Let us know if it works with 1 card

If you can post with 1 VGA card then the PSU either doesnt have enough power on the rail, or the card was not fully inserted.

The red light usually means that the card is not in securely, my ASUS motherboard also has that feature.
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August 5, 2010 1:08:37 AM

Hmm, is your red light for 'not in securely' a quick flash or constant?
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a b ) Power supply
August 5, 2010 1:16:34 AM

mine will go off if there is power to the mobo (if its off) and it is not inserted fully, its a solid red. I have a older Core 2 motherboard so they may have changed the error readout. Did you check your motherboard manual?
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August 5, 2010 9:25:31 AM

My mobo manual seems to lack an error led readout as well as beep codes. The beep codes were easy enough to find online, but if anyone finds the error readout somewhere it could be quite helpful. (I could not find it myself).

The manual only says that the red leds quickly light up to help you pinpoint the problem.

I should be troubleshooting with the suggestions in this thread (re-arrange cables, 1 GPU only, etc) tomorrow, if anyone wants to know. Hopefully I do not need a new PSU to handle the SLI amps!
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a b ) Power supply
August 5, 2010 1:58:08 PM

I found what the beeps mean in a motherboard manual online (support.asus.com)



Which if any of these LED's light up?

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August 5, 2010 7:47:01 PM

It was a quick red flash from the VGA_ led for sure, and I am somewhat sure that none of the other leds lit up, though I could be wrong since the scythe mugen 2 is huge and obstructive.

My plan tonight is to run it again the way I have it set up now to be certain of the problem, switch the power cords around to see if it helps, and then try only one GPU.

Edit- Wait, does the first diagram refer to beep codes or error leds? My internal speaker has yet to come in the mail but should be here soon.
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a b ) Power supply
August 5, 2010 9:17:45 PM

that diagram refers to your motherboard it was in an obscure place in the manual
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August 7, 2010 2:26:40 AM

Hello everyone, I entirely redid the PSU cables and chassis cables for better cable management. I also redid the GPU cables so that all the power would not come from one strand, and then tried booting up with one GPU only. The green standby power turns on, and then after turning on the case power nothing turns on except a quick VGA flash.

Thanks for all the help and please continue trying to help me boot this computer succesfully for the first time.
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a b B Homebuilt system
a c 83 ) Power supply
August 7, 2010 2:48:13 AM

Try the other GPU. Perhaps one is dead?
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August 7, 2010 2:56:53 AM

Oops, I gave you guys some misinformation. Actually there are three leds lighting up: the VGA_led, CPU_led, and boot device led. It was hard to notice these before I did all my cable management. These all light up at once with a quick flash when I press the case power switch. The only led NOT lighting up is the RAM.

Also, I received my 4 pin speaker today and plugged it in, and it made no noise during my boot up attempt.

4745454b, I will try your suggestion of trying the other GPU alone later.
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a b B Homebuilt system
a c 83 ) Power supply
August 7, 2010 4:10:50 AM

If the RAM LED doesn't light up its probably a RAM issue? I doubt the other card would make a difference in that case.
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August 7, 2010 4:21:08 AM

I think you might be right. Should I try the memOk function?

Edit- MemOk sadly failed to start the boot.
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August 7, 2010 8:29:05 AM

Sorry for the double post, but here is a picture of my newly assembled computer:



Hopefully this might help with troubleshooting, but if any of you want a more specific photo I will be happy to oblige.
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August 9, 2010 2:20:07 AM

I thought I would let you guys know that trying one stick of RAM did not help. I have basically tried everything in the troubleshooting guide except breadboarding and looking beneath the MOBO.

I am at the point now that I almost think it would be best simply to have a tech look at it, but if anyone has suggestions for troubleshooting I will take them.
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a b B Homebuilt system
a c 83 ) Power supply
August 9, 2010 2:31:24 AM

Can you borrow some ram from a friend? Just to test with different ram. Some systems dont' like some ram, perhaps this is the case here? Long shot, but best I've got.
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August 17, 2010 5:54:16 AM

Hello, I decided to pay 40 dollars for a professional diagnosis, and it turned out to be a faulty motherboard. The installation was done without error. I can simply RMA the motherboard. I just wanted to thank everyone for the help they have given me, and have decided to give the best answer to 4745454b since he answered the original question very well.

Thanks again for the help everyone!
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August 17, 2010 5:55:08 AM

Best answer selected by kerryking.
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!