4 Pin Plug for a 8 Pin MB Plug

[Oakind]

I need some clarification.

I have a Powersupply with a 4 pin male plug for the MB but the Motherboard I want has a female 8 pin plug.

Not all MB's have the 8 pin, most I look at have the 4 pin connector,

Will a 4 pin PS power the 8 pin MB plug? Or would I need a n adaptor ot a new PS?

Most people I speak with give different answers.

Thanks.

 

[VirtualLarry]

The 4-pin ATX12V connector will fit into half of the 8-pin socket. It will be fine.

 

[Oakind]

Thanks for your reply.

I was at comp USA today and asked a "tech"- and he started explaining its like running a car on the donut tire, it'll work, but not for too long.

I just needed to know if either it will work or not.. I just left the store. :roll:

Needless to say, thats why I posted here. I needed an informed answer.

 

[Oakind]

I found an answer to this question. Sounds like the CompUSA tech was correct.

You can plug a 4 pin 12 volt power cable into an 8 pin EPS motherboard connector but there's no guarantee that it will work. If the motherboard expects only one 12 volt rail then a 4 pin 12 volt cable may work. If the motherboard expects two 12 volt rails (many dual CPU motherboards require one 12 volt rail per CPU) then it won't work. Even if the motherboard works with a 4 pin 12 volt cable, you are still only providing half of the current carrying capacity which would be provided by an 8 pin EPS cable. That can overheat both the motherboard connector and 4 pin cable. Scorched or melted connectors can be a result. A motherboard which has the 8 pin EPS connector expects a lot of current and you are taking a serious risk by plugging in a 4 pin cable. The 4 pin cable only fits at one end of the 8 pin EPS motherboard connector so you can't plug it in improperly. That is, it only fits into one end of the motherboard connector unless you force it. If the cable doesn't go into the socket easily then you're probably trying to plug it into the wrong end. But then again, it's not a good idea to try to run with a 4 pin cable in an 8 pin motherboard anyway.

 

[VirtualLarry]

The difference between the 4-pin 12V and the 8-pin 12V is current carrying capacity. The 8-pin is NOT two 12V rails, it's still only one rail. There's a limit to the amount of current that any single wire can carry (without heating up). Twice the wires means twice the current capacity. 8-pin 12V starts to become useful at (IIRC) 120W (10A @ 12V) CPU power draw or greater. So it depends on what your chip is, whether or not you need the 8-pin PSU connector or not. Unless you are planning on overclocking a quad-core, then the answer is likely to be probably not.

 

[M1A]

Try this: http://www.outletpc.com/c8141.html

 

[nerp]

The CompUSA guy is wrong, IMHO.

I've used PSUs with the 4 pin connector in 8 pin slots with no problems for lengthy periods of times. There's a reason the notch is aligned such that both 4 pin and 8 pin connectors are usable. If this was a hack or something to be advised against, you wouldn't see so many 4-pin PSUs on the market and that notch would be in a different place.

 

[vj8usa]

Originally posted by: Oakind
I found an answer to this question. Sounds like the CompUSA tech was correct.

You can plug a 4 pin 12 volt power cable into an 8 pin EPS motherboard connector but there's no guarantee that it will work. If the motherboard expects only one 12 volt rail then a 4 pin 12 volt cable may work. If the motherboard expects two 12 volt rails (many dual CPU motherboards require one 12 volt rail per CPU) then it won't work. Even if the motherboard works with a 4 pin 12 volt cable, you are still only providing half of the current carrying capacity which would be provided by an 8 pin EPS cable. That can overheat both the motherboard connector and 4 pin cable. Scorched or melted connectors can be a result. A motherboard which has the 8 pin EPS connector expects a lot of current and you are taking a serious risk by plugging in a 4 pin cable. The 4 pin cable only fits at one end of the 8 pin EPS motherboard connector so you can't plug it in improperly. That is, it only fits into one end of the motherboard connector unless you force it. If the cable doesn't go into the socket easily then you're probably trying to plug it into the wrong end. But then again, it's not a good idea to try to run with a 4 pin cable in an 8 pin motherboard anyway.

Odds are you aren't using a dual CPU board. You'll probably be fine; I ran my main rig like this for a while (I only changed PSUs because my old one couldn't handle my new video card; I never had issues with the mobo power).

 

[nobodyknows]

How about using a 20 pin power connector on a 24 pin board?

I see they even make adapters for that.

http://www.outletpc.com/c6603.html

I'm looking at buying a used 680i mobo and am wondering if I can get buy using my old 550 watt PSU with 34 amps on the single 12v rail?

 

[Oakind]

Thanks for all the responses.

I called Gigabyte and talked to tech support and they recommedned against using a 4 pin PS on their 8 pin MB's due to the power requirements (current) of a Quad core chip. I really liked the Giga boards and used them in a few previous builds. But I have a new PS and hate to throw 90 bux on something I do not need.

I went and bought an ASUS M3A78-T motherboard as it has a 4 pin MB connector. The board is pretty nice, lots of options, plugs, connectors and should work out nicely.

I will be running a quad core AMD 9600 and want load the case up with lots of goodies and I don't want power to the chip to be an issue. Most power supplies I've seen have 4 pin connectors for the MB. 8 pins are rare to find and $90 and up- very pricey..

Ironically, Newegg combo deals pair a 8 pin MB with 4 pin PS's, which I find kind of funny.

For all you hot deal hunters, I bought the Asus off EBay for $141 ($11 shipping) and will get 25% cash back with Microsoft Live Cashback. The seller was the Ebay store of MWave.com, so the final price was better than CompUSA's $169 + tax and Neweggs $149 + 9.99 shipping.

Thanks for all the input. :beer:

 

[RAJOD]

Not sure why the gigabyte guy said not to do it.

Look at this intel MB (I own one) it has one 4 pin connector for the CPU.
It is made dual or Quad. Seems that intel things that 4 pins can run a quad.

I think that 8 pins may be better and have less heat per pin if overclocking a quad heavily. To get a 4 pin to actually melt, well I don't know how many amp or watts that would be but its probably well over 120.

http://www.intel.com/Assets/Image/prodlarge/DG45ID.jpg

Also you can use a 20 pin connector on a 24 pin MB. The extra 4 are used to distribute the current over more wires. If you are not running SLI its probably not needed.

Don't bother with a 20 to 24 pin adapter its not needed. Just plug the 20 pin directly into the MB leaving 4 pins unused. The adapter does nothing to lessen the load per wire up to the adapter. It will lesson the load from the adapter to the MB. It lessons you power some via added resistance.

I used one and had problems, pulled it out and problems of shutting down solved.

 

[tcsenter]

If the CPU is less than ~130W TDP, the 4-pin should be fine. If higher, you should really use the 8-pin.

 

[RAJOD]

Do you see any reason why you can't use a unused molex with an adapter to fill the other 4 pin power slot? Its 12 volts and if on a PC power n cooling the 12v is all on ONE rail.

As long as you don't have 4 HDs daisy chained on the same molex it probably would help distribute the power.

 

[o1die]

My compaq presario came with a 20 pin power supply on a 24 pin connector; it's been running fine for over a year.