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 Post subject: What's the 4 pin 12V connector for on my Athlon XP mobo?
PostPosted: Thu Jul 07, 2005 6:28 am 
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I've just had to buy a replacement mobo for my Athlon XP system. My previous board did not have this connector. I thought that it was only necessary for Pentium 4's.

The mobo I have just bought is an Abit AN7 NForce 2.

Should I use this connector or not? I remember something in the dark and distant past about ppl not using these for some coil whine reason.

Any thoughts ppl?

Thanks :)

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PostPosted: Thu Jul 07, 2005 6:36 am 
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Well, my cheapo motherboard requires that I do plug in the P4 connection, even though the CPU is a Athlon XP-M 1900+. I've heard of other people that don't need the P4 connector with an Athlon XP 2500+, so I guess it depends on the motherboard.

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PostPosted: Thu Jul 07, 2005 6:37 am 
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You must use it, as this square four-pin connector is where the CPU gets it's power (+12V). If your previous board didn't have this connector, then the CPU got it's power from the +5V line.

All Abit NF7/AN7 boards have the the four-pin ATX12V connection...

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 Post subject:
PostPosted: Thu Jul 07, 2005 10:41 am 
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Thanks for that. I guess I will use it then! :D

The more I think I know about PCs, the more I realise there is to learn!!! :roll:

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 Post subject:
PostPosted: Fri Jul 08, 2005 9:19 am 
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Why do CPU's need power from the 12V line now? The Vcore is ~ 1.4V, right?

I've had several socket A boards (2 different MSI VIA boards, a shuttle board, 5 ECS K7S5A's, an ABIT VIA), and none of them used any extra power connectors. Only my a64 board uses an extra connector.


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 Post subject:
PostPosted: Fri Jul 08, 2005 9:44 am 
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On Athlon XP boards, its not usually the Processor than needs the 4-pin 12V connector but rather the chipset. USually only nForce2 boards need the connector, in order to power the more powerful chipset.
If your board has one of these connectors you must use it or the board will not POST.

As far as why the CPU's need the extra power: the vcore does not tell the whole story, you must look at the totally Watts drawn by the chip. I forget the exact formula used, but you must multiply the vcore by something else to calculate the power draw of the chip.[/u][/b]

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 Post subject:
PostPosted: Fri Jul 08, 2005 10:05 am 
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luminous wrote:
The more I think I know about PCs, the more I realise there is to learn!!! :roll:

Amen!! to that Brother... :lol:


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 Post subject:
PostPosted: Fri Jul 08, 2005 12:04 pm 
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jamesm wrote:
Why do CPU's need power from the 12V line now?


The move to the 12V-line was made in version 2.1 of the ATX Specification because:
Quote:
3.3.2 Power Input

Power distribution trends are driving a change in the board power input connectors. As processors become
faster and more highly integrated, more current is required. To reduce power distribution loss, board
manufacturers are moving toward 12V power distribution. To facilitate 12V distribution to the processor
voltage regulator, a 2x2 connector will be required on these systems...


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 Post subject:
PostPosted: Fri Jul 08, 2005 12:49 pm 
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Consider that a processor pulls 100w. If using 5V, this means that 20A would be drawn from the power supply. However, because of the higher voltage, it would only be 8.3A at 12V. Keep in mind that amperes and heat are related. With higher voltage but lower amps, manufacturers can safely use smaller/fewer wires and lower amperage circuitry.

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 Post subject:
PostPosted: Fri Jul 08, 2005 4:27 pm 
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Yes, but there are no increasing power requirements for Socket A processors, since there are no new Socket A processors coming out (Athlon XP's rebadged as Semprons do not count, in my book). So why bother changing from +5V to +12V circuitry for the CPU?

Because ever since the introduction of the Pentium 4, power supplies have been shifting their circuitry towards +12V, away from +5V, for the reasons stated above. Socket A motherboards have been changing not so much to adapt to the new CPUs, as much as to adapt to the new power supplies.


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