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Sandy Bridge i5-2500k with 4-pin CPU Power Connector

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a b V Motherboard
March 16, 2011 5:18:19 PM

In a few months, I'm planning to pick up a Asus P8P67 Pro and a i5-2500k. My existing power supply (PCP&C Silencer 470) has only a 4-pin CPU power connector. I have done several searches and many have asked whether this will do. What I haven't been able to find is someone saying "Yes, I'm using the 4-pin cpu connector with the 2500k and it's working just fine."

For its part, Asus' P8P67 manual suggests that either an 8-pin or 4-pin is acceptable, but it's just a picture showing how to do it in either scenario. There is no documentation.

To cut unwanted responses off at the path, understand that 470w is not a lot. However, since the i5-2500k is overkill for almost any game I'd want to play in the next few years I'm not looking to overclock immediately, so the Silencer 470 will last me for a while.

So the question: Is anyone currently powering a 2500k or 2600k (or any of the other Sandy Bridge i5s or i7s) with only the 4-pin CPU power connector?
a c 716 V Motherboard
a b à CPUs
March 16, 2011 5:24:20 PM

I'd get a new PSU, you should use a 'real 8-pin' from your PSU especially if OC is the 'goal' by the assumption of your 'K' CPU.

However, there is an adapter 4-pin -> 8-pin. This will stress your PSU longterm.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

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a b V Motherboard
March 16, 2011 5:27:40 PM

jaquith said:
I'd get a new PSU, you should use a 'real 8-pin' from your PSU especially if OC is the 'goal' by the assumption of your 'K' CPU.

However, there is an adapter 4-pin -> 8-pin. This will stress your PSU longterm.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://images10.newegg.com/NeweggImage/ProductImageCompressAll300/12-201-005-02.jpg


OC is the goal long-term. I will eventually purchase a new power supply, but I hate to toss a good power supply that will only be 7 months old by the time I go to Sandy Bridge.

Given this, how do you know the 4-pin will stress my PSU long term? There's a single 12V rail on almost all consumer power supplies. To suggest that the power supply is going to be worn-out by the current having to go down 2 wires (with the 4-pin) rather than 4 wires (with the 8-pin) seems, frankly, tenuous and superstitious. Reminds me of Comcast's suggestion that DSL is slower because coax is thicker than UTP...

I don't want to disregard your advice and want to emphasize appreciation for your quick response, but can you provide any documentation?
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March 16, 2011 6:09:27 PM

Unless half of the 8-pin is 'capped' by the Mfg chances are it won't run or run properly {depending on the MOBO's Phase circuitry design} with the 4-pin. Using an 'adapter' to split a 4-pin with {X} AMPS into an 8-pin with {X+} AMPS can work. I have NOT looked-up your PSU to 'see' how many AMPS the 4-pin is rated to draw nor the MOBO/CPU AMPS needed particularly with OC nor how many RAILS your PSU has -- I prefer (1)/single rail PSUs. If your PSU is a single rail, I assume it is not, then using an adapter shouldn't be an issue.

Next, if your GPU is equivalent to a GTX 460 {vanilla/average} then you're under the recommend 550~650W with OC.

I am anything if trying to scare you or in particular if you are somehow 'thinking' I am clueless about electrolytic capacitor aging. You need to determine Wattage requirement X 1.2~1.3. In other words 20~30% above minimum requirements otherwise your PSU will indeed - guaranteed - have a short lifespan and worst degrade performance if under sized. ZERO DOUBTS!
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a b V Motherboard
March 16, 2011 6:20:31 PM

Right now this power supply is powering a 84w prescott 2m. The 2500k pulls in 135w at full tilt -- and full tilt on a 2500k probably won't even be realized for a few years. We're talking another 50 watts, so an extra 4 amps on a rail rated at 26amps.

Anyway, the question is -- is anyone currently running a 2500k with a 4-pin cpu connector?
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March 16, 2011 6:37:28 PM

I've been running an i5 760 (TDP 95W) on a single 4-pin with no issues at all. The i5 2500k also has a TDP of 95W, so I don't see how it will be an issue. According to my Gigabyte mobo manual, you only need the 2nd 4pin connector for the 135W TDP i7 processors. If you are going to seriously overclock, you will also likely need the extra juice.
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March 16, 2011 6:39:17 PM

Just get a new PSU. From that PSU you coudl build a new system... and its successor.
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a b V Motherboard
March 16, 2011 6:40:30 PM

nitrium said:
I've been running an i5 760 (TDP 95W) on a single 4-pin with no issues at all. The i5 2500k also has a TDP of 95W, so I don't see how it will be an issue. According to my Gigabyte mobo manual, you only need the 2nd 4pin connector for the 135W TDP i7 processors. If you are going to seriously overclock, you will also likely need the extra juice.


nitrium -- bingo, thanks. Exactly what I was looking for. Don't know why I thought 2500k was 135watts......

What's your PSU wattage? You got a dual or single 12v rail?
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March 16, 2011 9:10:06 PM

fullofzen said:
nitrium -- bingo, thanks. Exactly what I was looking for. Don't know why I thought 2500k was 135watts......

What's your PSU wattage? You got a dual or single 12v rail?


My PSU is a 5 year old(!!!) Coolermaster 450W, dual 12V rails (rated at 12A and 10A continuous, or 18A and 16A burst) . Easily runs the i5 760, an OCed GTX260, 2 HDDs, and DVD. System draw at the wall at load (stressing both GPU and CPU) is only 275W, idle is about 120W.
I kept the PSU after upgrading the system from an AMD Athlon X2 4200+ (TDP 89W - barely lower than the quad core i5 760!).
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March 16, 2011 9:50:26 PM

An i5-2500K + GTX 260 (OC) = 450W
An i5-760 + GTX 260 (OC) = 450W Ditto

PSU requirements depend upon the CPU, GPU(s), OC, etc...

I Googled Asus P8P67 Pro + 4-pin CPU + i7 2600K = blown CPU

Ain't my rig ;) 
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March 16, 2011 10:05:21 PM

jaquith said:
An i5-2500K + GTX 260 (OC) = 450W
An i5-760 + GTX 260 (OC) = 450W Ditto

PSU requirements depend upon the CPU, GPU(s), OC, etc...

I Googled Asus P8P67 Pro + 4-pin CPU + i7 2600K = blown CPU

Ain't my rig ;) 


My Gigabyte mobo manual specifically states that a single 4-pin connector is sufficient for the 95W CPUs. Further, how does insufficient power blow up the CPU??? If the system power draw is too great, it's the PSU that will overheat and die, the PC components should be fine. Anyway, like I said, I wouldn't overclock my CPU on a single 4-pin, but no way is it being overloaded stock - it says right on the PSU itself that it will do 120W continuous (12V at 10A) on a 12V rail, that is clearly ample for a CPU drawing 95W peak load!.
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March 16, 2011 10:40:29 PM

I appreciate GA, it utilizes it phases differently than ASUS. Don't confuse TDP with actual CPU use wattage; see TDP http://en.wikipedia.org/wiki/Thermal_design_power the OP CPU will draw 110~120 Watts non-OC.

If your GA had 4-pins covered then you can get by with using 4-pin unless your CPU requires more. The potential problem is if the 8-pin is open some the MOBO's phase power controller 'might' not function properly. Per my initial post the ADAPTER solves this problem ($5).

I have no clue 'why' the OP blew their CPU ; I saw it several hours ago on http://hardforum.com I do recall it wasn't running 'properly' e.g. cores a replaced 8-pin PSU AND new CPU solved the problem.

I've posted here too...ooo long not to see 4 vs 8 pin issues before and the subsequent problems.

My Motto doesn't say Do it half a$$ ... is says "Do it Right..."

I don't care one way or the other what anyone else does with their rig, nor do I give Jerry-Rigged or Poor Advice.
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March 16, 2011 10:57:18 PM

Found the post -> http://hardforum.com/showthread.php?t=1581590&page=2

In the final post the OP had a Scythe 700W Stronger PSU which is an 8-pin.

I read the manual it doesn't state "use either a 4-pin OR 8-pin. It stated 4/8-pin which can just as easily mean 2 4-pins.
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a c 78 V Motherboard
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March 16, 2011 11:22:53 PM

Okay, NO I don't have a 2500 or 2600......

BUT, let me try to explain the electrical engineering principles behind the 4 wire vs 8 wire debate.....

If the power supply can produce the power (Amps...)

Then bottleneck is NOT the for 4 wires running from the power supply to the motherboard. The true bottle neck is the trace on the PCB itself.

Resistance is the culprit here and the heavy gauge wires from the power supply are VERY low in resistance. On the other hand, the flat, thin, metal traces on the circuit board are relatively very HIGH in resistance.

(this is true since the equation for resistance is heavily dependent upon the surface area of the conductor....)

So, the $5 four pin to eight pin adapter in NOT a patch or a band-aid but will work EXACTLY like a "true 8 pin connector" wired straight from the power supply (anyone who tells you different has only the tiny fractions in the 4th or 5th decimal place to back them up....)


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March 16, 2011 11:55:12 PM

^Don't disagree as long as the 4-pin from the PSU is sufficient for the Amps drawn by the CPU. Essentially what I said, my 'caveat' was/is the PSU rated EATX12 V 4-pin.

What are your thoughts on using ONLY 4-pin and NOT 8-pin? {edit: the OP is sporting a 470W PSU}

If: [PSU] 4-pin (split into 8-pin) rated Amps ≥ [CPU] power requirements
Then: Good.
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a c 78 V Motherboard
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March 17, 2011 12:11:06 AM

I believe the 4 pin vs 8 pin is really all about getting that last tiny bit in your overclocking.

My favorite motherboards are ASUS & Gigabyte. If you look at an particular motherboard, Gigabyte usually runs 8 pin connectors, and, for essentially the Same board ASUS almost always runs 4 pin.

Both boards meet all specs, have great warranties, overclock like crazy, and last a long time.......


SOOOOO, 8 pins is nice, but, I think it's more hype than substance.... (hey, even boards with 8 pin connectors most often "cover" the other 4 pins with a black plastic blank, so, it's Certainly OPTIONAL......

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March 17, 2011 2:22:15 AM

jaquith said:
^Don't disagree as long as the 4-pin from the PSU is sufficient for the Amps drawn by the CPU. Essentially what I said, my 'caveat' was/is the PSU rated EATX12 V 4-pin.

What are your thoughts on using ONLY 4-pin and NOT 8-pin? {edit: the OP is sporting a 470W PSU}


For sure, if I had an 8-pin I would use it. If my PSU had 2x4-pins, I would have used them both. Nothing wrong with providing extra headroom! The issue for me was that my (admittedly antiquated) 450W PSU only has a single 4-pin connector. But after looking at the TDP of my previous Athlon 4200+ which was successfully powered (and OCed from 2.2GHz to 2.6GHz) for 3-4 years (on a mobo that only had a single 4-pin header anyway), I had zero doubt that the same single 4-pin would also power my new system. This was verified in the mobo manual, which clearly states a 4-pin is sufficient for the 95W i5/i7's. In so far as it is practical I like to keep using my computer components for as long as they are fit for purpose. A single 4-pin is a 100% sure fit to power 95W TDP processors. It will not, however, give you much scope for overclocking!
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March 17, 2011 1:55:40 PM

As I've been TRYING to say, it all depends on how your MOBO is designed 'wired' to handle the incoming power and phases. The capping of 4 of 8 pins is a tell tale 4 or 8 is fine; obviously depending on the power requirements.

Clearly, my first post -- the "adapter 4-pin -> 8-pin" for $5 is the safest option to your expensive CPU. On my i7 it simply will NOT post with the use of the 4 of 8 pins. In addition, I've seen plenty of 4 vs 8 pin failures in Toms. It may work fine, it may 'seem' fine, it may damage the CPU, or it may fail all together. I take the safest option.

Honestly, I DON'T CARE what people do, I've stated my peace.

Pin 1 -> Phase
Pin 2 -> Phase
Pin 3 -> Phase
Pin 4 -> Phase
Pin 5 -> Phase
Pin 6 -> Phase
Pin 7 -> Phase
Pin 8 -> Phase

Pin 1 -> |
Pin 2 -> |
Pin 3 -> |
Pin 4 -> |
-> Phase bank
Pin 5 -> |
Pin 6 -> |
Pin 7 -> |
Pin 8 -> |
-> Phase bank

Pin 1 -> |
Pin 2 -> |
Pin 3 -> |
Pin 4 -> |
Pin 5 -> |
Pin 6 -> |
Pin 7 -> |
Pin 8 -> |
-> Phase bank
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March 17, 2011 6:57:22 PM

jaquith said:
Honestly, I DON'T CARE what people do, I've stated my peace.


Deep down you know you DO care. Else you wouldn't be posting so many replies here in the first place! ;) 
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a b V Motherboard
March 17, 2011 9:39:25 PM

Best answer selected by fullofzen.
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a b V Motherboard
May 26, 2011 10:50:13 PM

I know I'm reopening an old thread here, but wanted to post a conclusive answer of my experience on this. Since Tuesday, I have been running a P8P67 (plain-vanilla version; no pro) with a i5 2500k with only the 4-pin power connector provided by my PCP&C Silencer 470 PSU. I did some modest overclocking (40 multiplier; auto-voltage) and the system ran perfectly stable with Prime95 -- if a bit too hot with stock cooler (hyper 212+ on the way as we speak) and the excessive Asus-engineered auto-voltage -- with only the 4-pin power connector.

As a note, the 4-pin CPU power cord is too short to reach comfortably to the 4-pin connector when mounted at the bottom of this case (it was built for a case with both the power connector and the power supply at the top of the case) and hangs awkwardly over the video card. As a result, I have indeed ordered the 4-pin to 8-pin converter as a means to extend the length and avoid infringing upon the GPU's personal space.

I am also sympathetic to jaquith's suspicion that the PCB's "power paths" between the power connector and the voltage/phase regulators may be set-up with a 8-pin connector in mind (less power over more lanes). However, it does not seem strictly necessary for the motherboard to run to have 8-pins connected -- I just don't know how to test this hypothesis without a 5 year study.
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June 1, 2011 2:18:24 AM

fullofzen, I hate to tell you this but I blew my first P8P67Pro board up because of a 4 pin connector in the 8 pin socket.
The lanes on the motherboard burned out.
Very smelly.

To the OP.
Get a 4*12v rail modular supply and feed one of them exclusively to the CPU via all 8 pins, it's the only way to be sure.
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a b V Motherboard
June 1, 2011 3:27:34 AM

CtJackal -- interesting. I certainly appreciate you providing the input. (I am in the OP, btw). A few questions, actually:

1) What chip were you running? Were you OC'd?

2) What PSU were you using? Did it end up damaged or is it fine?

3) What was the computer up to when it failed? Were you running a full-load with prime95 or something?

3) How can you tell that the 4-pin set-up was what caused the issue? You mentioned that the "lanes on the motherboard burned out." Did you happen to take pictures? I'm really curious of what they would have looked like.
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June 1, 2011 2:32:38 PM

Hi fullofzen, it's a 2500k and yes it was overclocked to 4.6ghz at the time.
The PSU is a cheap generic 500W supply which amazingly still works although I have no confidence in it after the hammering it took.
I was showing off my overclock to a friend and span the cores up with Prime95, I had done this previously for a couple of hours with no ill effects, this time there was an almighty POP after about 10 minutes.
The reason I assume it was the 4 pin connector is that I initially tracked the location of the failure by smell, the burnt component/ozone pong was concentrated around the ATX 12V connector and when I removed the 4 pin plug there were scorch marks actually inside the socket.
I have to admit I didn't see any blackened traces on the motherboard but needless to say it never worked again.
The yellow power LED would light up but when I pressed the power button it would "tic" the fans and then nothing.
Exactly the same behaviour that a motherboard exhibits when it has no ATX 12v connected :/ 



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June 1, 2011 2:38:26 PM

One thing I will add is that after buying a new PSU (OCZ Fatal1ty 750W) and RMA'ing the motherboard I need far less volts for the same overclock.
Previously I needed ~1.45v to get 4.6ghz, now the same CPU is perfectly stable at 1.25v.
Whether this is a consequence of the smoother current I don't know but it's the same CPU and the same model motherboard so it would suggest that a proper 8 pin connector on a dedicated PSU rail is better than a shared single rail with a 4 pin connector when it comes to CPU voltage requirements.
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a b V Motherboard
June 1, 2011 3:54:30 PM

I think it is more likely that your acknowledgely-cheap no-name power supply shorted temporarily and that's what fried your motherboard. I find it hard to believe that there would be a sudden failure of the motherboard lanes related to using a 4-pin connector. Maybe a failure over years with BSODs every so often, but a catastrophic failure? That doesn't make sense.

I'm going to say that that was probably your PSU itself causing trouble. There's no other way to explain it.
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June 1, 2011 6:25:57 PM

jb6684 explaination was excellent and true. But there is a worst culprit than the circuit board traces and the primary reason for adding the 2nd pair of 4 wires to the ATX connector. And that is the connector itself. The contact resistance between the Male/female pins is much higher than either the wires or the circuitboard traces and therefore the highest IsqR Loss - all in the form of Heat.
Quote from CtJackal: "...When I removed the 4 pin plug there were scorch marks actually inside the socket"
I've seen a couple of other posts indicating the the plastic around the connector has melted.

This resistance also has a problem with oxidation over time (oxidation increases the resistance). Another problem deals with the quality, either the MB connector or the PSU connector which results in a poor fit and therefore higher contact resistance. Side comment: Silver is a better conductor, but never used as it is the worst for Oxidation, Copper 2nd best conductor, but also has an oxidation problem, gold plated - Gold is a 3rd rate conductor, but has 2 advantages - Slower oxidation and it is "slippery" meaning that contact pressure can be increased and still allow matting for us non 800 Lb gorillias.

Before I carry on. jaquith Has a good point - it's how the MB is laid out, Does each trace go to a dedicated VRM, or are the traces Shorted, either at the VRMs, or at the Socket - prefered. Easy to tell Just ohms check the pins at the ATX connector, if all red wires read 0 ohms to each other, they're short at one end or both.

For CPUs under 120 W (10 amps on 12V line), excluding what jaquith indicated on Phases, the 4 pin is fine, 8 pin better as IR loss at the connector is lower. The adaptor is fine also. The advantage of true 8 pin connection is that there is "Slightly" higer voltage at the VRMs, they do not have to work as hard - Very small positive, but as jaquith pointed out - ANY improvement is better.

For CPUs > 120 Watts eight pins should be used, And here I will disagree with jb6684 "EXACTLY like a "true 8 pin connector"", Not true, Yes at the motherboard it will see a "TRUE" 8 pin connection, ie the total current thru each pin will be I(total)/4. However you have added injury to insult. You still have the 4 pin connection, not on MB but at the PSU connector (injury) and you have added another connector with the added contact resistance (the Insult).
Hope I don't fall in your catagory of "(anyone who tells you different has only the tiny fractions in the 4th or 5th decimal place to back them up....)"
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