Using a 6pin and half of a 4pin for 8pin CPU power on new mobo?

Well, first you get the annoying lecture : If you are building a new system the power supply is the LAST thing you want to skimp on. You should buy a new, modern PS for the system.

Now that's out of the way.

There is nothing technically wrong with how you want to do it. The power supply delivers 12v to each yellow wire regardless of where they actually go. So if the MB needs four 12v wires (and 4 black grounds) to run you can accomplished that your way.

There could be a problem - resulting in odd behaviors and system problems - if the 12v leads came from different 12v rails on a multi-rail power supply. This could result in "dirty power", where the amperage (as opposed to voltage) is not the same across all 4 wires at the same time. This could even happen in a single rail system, depending on the internal circuitry of the PS and where those two separate wire bundles connect.

The only thing that concerns me from your picture is that 3 of the yellow wires are in the back row and that one (plus the extra one hanging off) is in the front row. This seems to be a problem with polarity and I am surprised the system runs like that. I think that all 4 yellow wires should be in all the rear slots.

Try the first adapter in this list at NewEgg

Newegg.com - Computer Hardware, power supply adapter

As bobkn said, your power supply should come with a 4+4 pin connector. They are split because some boards only use a 4 pin and some use an 8 pin. By being split int 2 4 pins, they can be used on either. This is what they look like and you should have one. You will also notice they have a clip on each one. Feel where they plug in. One side will have a ridge on it. That is where the clip goes, just so they are oriented correctly.

I appreciated all of the responses.

Earlier today I ordered Newegg.com - Rosewill 9.5" EPS 8-Pin Male to ATX 4-Pin Female Cable with Cable Sleeve Model RCA-RU9.5-P8M-P4F to try and resolve this issue. Will that work?
EDIT: Also, you'll see in my response that I keep saying the two 4 pin connector combined don't form the right connector for the 8 pin female for the CPU on the motherboard so I've attached a couple pictures of my two 4 pins held next to each other so you can see what I mean.

My listed specs are for my current computer until I finish this new build. The new build contains:
Newegg.com - Thermaltake Armor A90 Gaming Mid-Tower Chassis With Cable Management Water Cooling SSD Support And Tool-Less Installation VL90001W2Z

Newegg.com - COOLER MASTER GX Series RS650-ACAAD3-US 650W ATX12V v2.31 80 PLUS BRONZE Certified Active PFC Power Supply

Newegg.com - BIOSTAR TZ77B LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS

Newegg.com - Intel Core i5-3570K Ivy Bridge 3.4GHz (3.8GHz Turbo) LGA 1155 77W Quad-Core Desktop Processor Intel HD Graphics 4000 BX80637I53570K

Newegg.com - ADATA XPG Gaming Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model AX3U1600GC4G9-2G

Newegg.com - Corsair Force Series 3 CSSD-F90GB3-BK 2.5" 90GB SATA III Internal Solid State Drive (SSD)

Newegg.com - LG Black 10X BD-ROM 16X DVD-ROM 48X CD-ROM SATA Internal 12X Internal Blu-ray Drive 3D Playback & M-DISC Support Model UH12LS29 LightScribe Support - Blu-Ray Drives

Newegg.com - Palit NE5X460SF1102 GeForce GTX 460 (Fermi) Sonic 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

Newegg.com - Creative Sound Blaster Audigy SE 7.1 Channels 24-bit 96KHz PCI Interface Sound Card

TVeblen said:

Well, first you get the annoying lecture : If you are building a new system the power supply is the LAST thing you want to skimp on. You should buy a new, modern PS for the system.

Now that's out of the way.

There is nothing technically wrong with how you want to do it. The power supply delivers 12v to each yellow wire regardless of where they actually go. So if the MB needs four 12v wires (and 4 black grounds) to run you can accomplished that your way.

There could be a problem - resulting in odd behaviors and system problems - if the 12v leads came from different 12v rails on a multi-rail power supply. This could result in "dirty power", where the amperage (as opposed to voltage) is not the same across all 4 wires at the same time. This could even happen in a single rail system, depending on the internal circuitry of the PS and where those two separate wire bundles connect.

The only thing that concerns me from your picture is that 3 of the yellow wires are in the back row and that one (plus the extra one hanging off) is in the front row. This seems to be a problem with polarity and I am surprised the system runs like that. I think that all 4 yellow wires should be in all the rear slots.

Well I hadn't tried running the system as shown in the picture when I posted this. I did try running it with just a 4 pin connector in half of the 8 pin female as I read somewhere this may work but I received a short beep upon boot and no video signal from onboard video or from my GTX 460 so I assumed no POST. All fans and devices were running except for the CPU fan which struck me as odd. For comparisons sake I unplugged the CPU power all together and turned on the system which resulted in immediate shutdown, which, from my understanding, is supposed to happen.

kbrady1979 said:

The 4+4/8 pin EPU is DIFFERENT from say a PCI-e type connector for example. The EPU should have 4-12v wires and 4 ground wires and the PCI-e only uses 3 and 3. Also to be noted, an 8-pin PCI-e doesn't use 4 and 4 either, it uses 3-12v wires and 5 ground wires. Either use 4+4/8 pin EPU cables/extensions for the sake of your CPU.

I just reread your first post and noticed your PSU doesn't seem to have a 4+4 or 8 pin EPU, is that correct? If it doesn't, buy a PSU that does.

It has two 4 pin connectors, one of which I used on my old motherboard to power the CPU as it was only 4 pin, but combined they do not create the same plug as needed for the 8 pin CPU power. Though on Newegg (Newegg.com - COOLER MASTER GX Series RS650-ACAAD3-US 650W ATX12V v2.31 80 PLUS BRONZE Certified Active PFC Power Supply) the PSU I have does list a 1 x 4+4-Pin ATX/EPS 12V connector.

bobkn said:

XGamer95 said:

I'm in the middle of assembling a new computer (first one) and I just realized that my current PSU does not have an 8-pin ATX power connector for the CPU on the motherboard. Is it safe to use a 6-pin and half of a 4-pin connector to power the CPU? I've attached a picture and as you can see half of the 4-pin is just hanging off the end.

What's your PSU? The one listed in your specs is a 650W Coolermaster GX. CM claims that it has a 4+4 pin ATX +12V connector.

I'm not up for checking the pinouts to see whether what you're attempting is sane or not. Connecting +12 to ground might have unfortunate consequences. (Got a fire extinguisher handy?)

The normal approach would be to use a 4 pin +12V connector, if that's all you have. (Some of the motherboards I've used in the past couple of years came with caps on half the 8 pin socket.) It might not provide all the current that you'd need for a high powered (125W) CPU.

The exact PSU I have is here: Newegg.com - COOLER MASTER GX Series RS650-ACAAD3-US 650W ATX12V v2.31 80 PLUS BRONZE Certified Active PFC Power Supply It does say it has 1 x 4+4-Pin ATX/EPS 12V connector but combined they do not form the correct plug for the 8 pin female on the motherboard. I did try with only a single 4 pin but I received a short beep upon boot and no video signal from onboard video or from my GTX 460 so I assumed no POST. All fans and devices were running except for the CPU fan which struck me as odd.

essenbe said:

As bobkn said, your power supply should come with a 4+4 pin connector. They are split because some boards only use a 4 pin and some use an 8 pin. By being split int 2 4 pins, they can be used on either. This is what they look like and you should have one. You will also notice they have a clip on each one. Feel where they plug in. One side will have a ridge on it. That is where the clip goes, just so they are oriented correctly.

I do have those but combined they do not form the correct connector for the 8 pin female on the motherboard. They are not mirror images of each other as would be required for them to work.

Your converter cable is a good solution and will work to accomplish your task and you could go that route.

But here's the thing: you are converting a legacy power supply to use in a modern system. Yes, it's a new old power supply. Wouldn't it make more sense to take your time and get the right parts?

You should return the CoolerMaster ATX power supply and get the correct ATX12V v2.31/ EPS12V v2.92 power supply that has the 8-pin connector on it.

Here are a couple of nice units that are the same price and wattage:

Newegg.com - CORSAIR Enthusiast Series TX650 V2 650W ATX12V v2.31/ EPS12V v2.92 80 PLUS BRONZE Certified Active PFC High Performance Power Supply

Newegg.com - SeaSonic M12II 620 Bronze 620W ATX12V V2.3 / EPS 12V V2.91 SLI Ready 80 PLUS BRONZE Certified Modular Active PFC Power Supply