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4 pin ATX 12v vs 8 pin ATX 12v

post #1 of 11
Thread Starter 
I don't understand why some mobos have 2 x 4 pin and others 1 x 4 pin.

Like the M4A79XTD EVO has only 1. (129.99)

and the GA-790XTA-UD4 has 2. (149.99)

Yet they both seem to support the same range of chips and both support up to 140w chips (Unsure if this is related to my question) What advantages does a board have with 2 x 4 pin 12v connectors?

Why I ask is because I once had a mid tier Asus board that had a throttling problem under load, and when I switched to the Gigabyte board I now have in my sig rig the problem disappeared.

Now my GA-MA770T has died (Prime killed it) and I'm shopping for a new board (while I rma this one) and it's come down to one of these two. But I'm really afraid of having the same problem I had with my first Asus board.

Any answer to the question would be appreciated, and a suggestion on which board of the two would be cool too.

Oh and I know the boards are cheaper at e-tailers but I need it TONIGHT.
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post #2 of 11
Simply that they can provide more power to the CPU socket if need be.

Get the 790XTA-UD4. It's a proven clocker.
    
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post #3 of 11
my board uses a 1x8 pin atx but it runs fine with a 1x4 pin atx. i think the extra power is for stability when overclocking?
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post #4 of 11
Thread Starter 
The M4A79XTD EVO is advertised as an overclockers board.

Is the general rule in order to get a REAL overclocking board from Asus you need to get a 200.00+ board? Cuz if thats the case... Asus is crap.
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post #5 of 11
Because they needed more amps on the 4 pin connector but they had to make a new connector so you wouldn't draw more amps when the rails weren't ready. The 8 pin doubles the amps and doubles the connection so it gives 4 times more power. But the 4 pin, if the power supply can deliver double the rated amps, which nearly all can do, then you have a hard time getting the processor to not go past the thermal limits of the package design long before a 4 pin runs out of juice.

You waste a couple less watts of resistance juice using an 8 pin that has low gauge wiring but power supplies come with such excellent wiring any more that's fairly moot.

I'm anal retentive with wiring losses. I use 6 gauge cable for my computer when it only uses 6 amp max and I use 3/8x3/4 copper bus bars that weigh a pound piece for my battery pack interconnects center tapping on every interconnect so that the voltage is exactly the same at each battery + or - a couple hundredths.
I have to say though most power supplies could stand to go up a gauge or two on the CPU and PCI connectors.
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post #6 of 11
Quote:
Originally Posted by doritos93 View Post
The M4A79XTD EVO is advertised as an overclockers board.

Is the general rule in order to get a REAL overclocking board from Asus you need to get a 200.00+ board? Cuz if thats the case... Asus is crap.
No. A single 4 pin goes out of spec at anything over 192 watts. The spec is 30 degrees celsius rise in the wire due to resistance. Some people make and sell cheap wire that isn't really as big as it's supposed to be to save on materials. You can buy 100 ft rolls of 4 gauge car amp wire that all you have to do is stick it on a scale to show that it's not 4 gauge it's really 8 gauge or 10 gauge.

So it's just a matter of circumstances. Where you put the wrong power supply on it and you got a burnt out rail down the line. Because you'd end up pulling 19 amps to feed that processor thats using 17.5 amps for a 210 watt overclock but heats the wire doing it. Honestly the same gauge molex connectors will give you 11 amp max and should give you 22 amp max for the 4 pin connector because your running it through 4 wires and it's using the same connector type and same gauge.
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post #7 of 11
Thread Starter 
Quote:
Originally Posted by Hephasteus View Post
No. A single 4 pin goes out of spec at anything over 192 watts. The spec is 30 degrees celsius rise in the wire due to resistance. Some people make and sell cheap wire that isn't really as big as it's supposed to be to save on materials. You can buy 100 ft rolls of 4 gauge car amp wire that all you have to do is stick it on a scale to show that it's not 4 gauge it's really 8 gauge or 10 gauge.

So it's just a matter of circumstances. Where you put the wrong power supply on it and you got a burnt out rail down the line. Because you'd end up pulling 19 amps to feed that processor thats using 17.5 amps for a 210 watt overclock but heats the wire doing it. Honestly the same gauge molex connectors will give you 11 amp max and should give you 22 amp max for the 4 pin connector because your running it through 4 wires and it's using the same connector type and same gauge.
Sorry, I'm having trouble understanding, but what you're saying is there is no difference between the 4 pin and 8 pin as long as you have the right PSU?

My PSU is a couple years old and I don't think it delivers as much current as these newer ones.



So my PSU delivers 18 A. Do you think that might be the cause of the CPU trottling under load with the single 4 pin connector boards?
Edited by doritos93 - 6/10/10 at 3:12pm
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post #8 of 11
Quote:
Originally Posted by Hephasteus View Post
Because they needed more amps on the 4 pin connector but they had to make a new connector so you wouldn't draw more amps when the rails weren't ready. The 8 pin doubles the amps and doubles the connection so it gives 4 times more power. But the 4 pin, if the power supply can deliver double the rated amps, which nearly all can do, then you have a hard time getting the processor to not go past the thermal limits of the package design long before a 4 pin runs out of juice.

You waste a couple less watts of resistance juice using an 8 pin that has low gauge wiring but power supplies come with such excellent wiring any more that's fairly moot.

I'm anal retentive with wiring losses. I use 6 gauge cable for my computer when it only uses 6 amp max and I use 3/8x3/4 copper bus bars that weigh a pound piece for my battery pack interconnects center tapping on every interconnect so that the voltage is exactly the same at each battery + or - a couple hundredths.
I have to say though most power supplies could stand to go up a gauge or two on the CPU and PCI connectors.
hmm i was planning on getting the MSI 890GXM G65 and it also uses 4-pin CPU connector. I was planning on using a corsiar HX650 to power my rig, would it be fine if I overclocked an x6 1090T to 4ghz?
Edited by Mr.Pie - 6/10/10 at 3:21pm
post #9 of 11
A motherboard with an 8pin will ususully have better CPU VRMS, Meaning it will be able to deliver more power to the cpu, But the actual 8pin would rarely matter with a good psu (Not cheap wires)
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post #10 of 11
Quote:
Originally Posted by doritos93 View Post
Sorry, I'm having trouble understanding, but what you're saying is there is no difference between the 4 pin and 8 pin as long as you have the right PSU?

My PSU is a couple years old and I don't think it delivers as much current as these newer ones.



So my PSU delivers 18 A. Do you think that might be the cause of the CPU trottling under load with the single 4 pin connector boards?
Ya you should be alright. If the 4 pin draws from 2 rails. An 8 pin can draw from 4 rails so it spreads the load out even further. A 1090T shouldn't pull over 175 watts anyway so I'd say definitely you would be alright. The problem is that as you get closer and closer to max amp draw through a wire you get larger and larger voltage drops. So the stability problem with intel cpu's comes from being up around 200 plus watts just outside of the spec and the cpu only seeing the minimum power the VR's can work with which puts them into efficiency overload. For instance one set of the VR on chip can deliver 12 amps at 12.0 volts but only deliver 11 amps at 11.85 volt.
You would definitely be outside of those kinds of issues with a 4 pin on a 1090t unless something was really screwy which it won't be with that board and that power supply.
Edited by Hephasteus - 6/11/10 at 5:34am
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