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P4 power supply backwards compatiblilty

By sdoetsch ·
I recently bought a P4 400W power supply on sale and didn't realize that these new power supplys have a power connector for the processor.
Can I use this supply on an older board (running an AMD K6-2 500mhz)and just leave the P4 processor power connector hanging or will the power supply fry my board?

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by CG IT In reply to P4 power supply backwards ...

umm I believe the K6-2 processor is a socket 7 and there are socket 7 ATX form factor mainboards. A ATX power supply will be compatible. Boards that are not ATX form factor but AT form factor have the 2 connector P1 & P2 power supply connector.

note: I've used power supplies that have the seperate 4 pin cpu power supply cable on boards that don't require a seperate power supply cable for the CPU. The use of a seperate power supply cable for powering the cpu is a mfg design layout. Mostly to circumvent circuit path tracing problems near the cpu socket.

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by TheChas In reply to P4 power supply backwards ...

The extra connector is simply additional 5 and 12 volt power supply lines.
These allow for the additional current requirements of newer CPUs.

I would be more concerned about the high wattage rating of the supply.
Unless you have a number of drives installed, a 400 watt supply has nearly twice the power capacity a supper socket 7 system needs.

Theoretically, all this means is that the power supply will not be working very hard, and will run much cooler than a 250 watt supply.

In practice, if the supply is poorly (cheaply) designed, it may have voltage spikes on the output lines when it starts up.
If there are spikes on the supply lines, it will be more of an issue for your drives than the motherboard.

Bottom line, if it is a name brand supply you should be fine.
If it is a no name supply and is noticeably lighter than other 400 watt power supplies, there "may" be some slight risk.

Chas

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by csmith In reply to P4 power supply backwards ...

We do this all of the time for clients, when the power supply goes bad in their PC.
The extra plug is just useless, in your case.
The minimum load on a power supply is 10% for a decent one, and as high as 25% for a cheap one.
When the load is too low, the voltage regulator becomes unstable, and the voltages go "above allowed values"
A "any one of" a newer AGP video card, a second hard drive, or a CD burner, will insure that there is sufficient load on a cheap power supply. Increased memory will give about 5 watts per stick, more load.
You have nothing to worry about if you have a quality power supply. You are already over 10%, even though AMD CPUs of this era are more energy efficient than the equivalent Pentiums.
Regards, Chris

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by rawright In reply to P4 power supply backwards ...

If the power supply has a connector that fits your AMD board, use it and don't worry about the P4 connector. Your MB should have a local voltage regulator that properly adjusts the raw power from the 5V/12V supply lines to whatever your MB and CPU require. The fact that the supply provides a 400W capacity isn't important; if your MB doesn't need it, it won't draw it. You may find the excess capacity handy, though, if you want to add a number of disk drives or cooling fans to your system.

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