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The mystery of the 24 pin motherboard

Last response: in Motherboards
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January 6, 2006 6:43:28 AM

I have a question for the real techies of the PC world. I am using an AMD 3000+ (939) in an MSI K8N Neo4-F nForce 4 (With a 24 pin power connector) and a Powercolor X800GT PCI-E. I bought a gaming bomb case and it came with a 24 PSU so no problems with the PC. The PC works fine and I haven't had any problems. So you're wondering what the problem is?

Ok, now what I don't understand is my friend bought the same PC but he got the X800 GT Extreme edition and some cheap case with a 300W PSU but it had a 20 pin connector on the PSU. He pluged it in (It fits into the first 20 pins but leaves the 4 on the end open) and his PC also works fine...

So my question is what is the point of a 24 pin connector if the PC works fine with only 20 being used? And what are the 4 extra pins for? :roll:

Any info on this issue would be most helpful!! Thanks
January 6, 2006 11:27:25 AM

I still need to find out what the 4 extra pins are for... I remember another PC I built that was based on the RS-480 chipset and it had a 24 pin but I put the 20 pin from the PSU in and it worked fine...
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January 6, 2006 12:04:46 PM

The extra 4 pins are for PSUs that use the EPS12V standard. The first 20 pins use the same wiring diagram as the ATX-12V standard, allowing an ATX-12V PSU to run a motherboard with an EPS12V connector. EPS12V PSUs can be used with an ATX motherboard via a cable adapter.

As far as I know, the EPS12V standard was developed for larger rackmount server motherboards - These systems could be running between 2 and 4 processors with lots of memory, which requires lots of power. The extra 4 pins were therefore added to spread the load across more wires, reducing the risk of burning out the PSU connectors.

There are also some 8-position supplimental power connectors out there
See this for an example of both: http://www.tyan.com/products/html/thunderk7xpro.html
Look for the red-highlighted note on the right side of the board spec and folow that link for a few more details.

Newer 64-bit processors, PCI-E, SLI graphics cards and other new hardware are also causing increased power demands, and therefore some motherboard makers are moving to take advantage of the (generally) heftier EPS12V PSUs.

Hope this helps.
January 6, 2006 1:15:01 PM

it means that for entry level systems, like a 3000+, you could just plug the 20 pin connector assuming the cables are good and the capacitators on the motherboard too. ( i think that a mobo like a8n32-sli using eight phase power feed could not do it... but who knows ).

also, if you plan on overclocking, or get a 4800+, a high voltage pc 4000 ocz vx ram, high end parts...
you should get not only a 24 pin PSU but a REALLY good one, branded

like a 350w antec from the 1650 cases beating
a codegen 550w
January 6, 2006 1:57:30 PM

Thanks of the help guys. I don't plan on getting any upgrades soon so I won't need to change anything! :wink:
!