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24-pin ATX Power on mobo using 20-pin plug from PSU

Sister-in-law gave me her old HP Pavilion a6314f desktop PC. It has an Asus M2N68-LA (Narra2) motherboard in it. AMD Athlon x2 64 5000+ CPU.

I'm going to use this PC as a second unit for my wife in our office, and as a stepping stone into a new Intel Core i7, or newer LGA1155, next year. I don't want to throw alot of money into this system, but plan on upgrade "things" in it, for use with a new build (i.e. future proof).

Already got an OCZ Agility 2 60GB SSD for OS/Programs, and pulled an Seagate 7200.11 500GB SATA II HDD out of a RAID 0 array in my rig for backups. Will use the original Seagate 7200.10 360GB SATA II HDD for data/media.

Up'd the RAM to 4GB, no problem, only $19.99 a 1GB DDR2-667 (PC-5300) stick, needed 2. I know this is a loss for future build, that's why I didn't up it to 4 or 8GB DDR2-800 (PC-6400) RAM.

Next, I would like to upgrade the video from the onboard NVidia 6150-SE GeForce 430 chipset (??) to a Radeon 5770. The new card will be future proof. BTW: the onboard graphics are rated 3rd from the bottom, and the new card 5rd from the top, in THG Graphics Card ratings/articles.

But, before I can install a PCI-E x16 graphics card, I need to upgrade from the 250W :lol: PSU in the case. Probably going to get a Corsair 650HX Modular PSU, to be future proof. (And for only a few bucks more, a new Antec 300 case, too.)

The question I have is this: the motherboard has a 24 pin ATX power connection on it, but currently the PSU only has a 20pin connector going to it. Will I fry the mobo if I plug in a "standard" 24 pin ATX power into it? The "extra" 4 pins on the mobo are just exposed, next to the 20 pin that plugs into it.

I know it's a P.o.S., but I don't have all the cash for a full new system right now. So I'm piecing one together.

BVW: I hate pre-built systems! Dell, Gateway, or HP! No customization, or overclocking. And their motherboards are non-standard unit, usually specific to the case the are in. Non-standard mobo connectors (USB, Case, Front Panel, etc.). Well, at least this HP unit looks like the mobo could go into a "after-market" case, and have all the case connectors work with the mobo. :sarcastic:
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  1. In theory, a 20-pin mobo PSU connector will work on a mobo with a 24-pin socket, but it's risky because the 20-pin connector may not provide enough power. What's the difference? Long ago, while PC's were still in their youth, the mobos were designed and built with only a 20-pin socket, this is due to the lower power/quality CPUs from the same era. As more powerful CPUs were invented, stability became an issue. Thus, the 24-pin socket was designed and incorporated.

    I assume you're referring to the 250 W PSU, as a 650 W w/ only 20-pin is odd. Secondly, I'd be cautious with building too much on to that 250 W PSU (if that is what you're using), with all those extra devices, you could be putting too much load on the low quality PSU.
  2. There is an adapter, but verify that you PSU has enough power. http://www.newegg.com/Product/Product.aspx?Item=N82E16812200064&cm_re=24_pin_to_20_pin_adapter-_-12-200-064-_-Product



    According to my calculations, you need at least a 450W+ PSU {Athlon x2 64 5000+, SSD + HDD, HD 5770, no OC}.
  3. To clearify:

    If I upgrade to a 650W PSU, will the 24-pin ATX power connector fry my mobo, as it only uses a 20-pin power connection from the 250W PSU now, even though it is a 24-pin connector on the mobo?

    Yes, I need to up the 250W PSU [if] I get a Radeon 5770, which requires a PCI-E connector, which the 250W doesn't even have. I doesn't even have SATA connectors, it has a Molex 4-pin to SATA 15-pin power adapter(s). I added a Molex to 2-SATA spitter, but I think I still have a open molex connector from the PSU.

    As is, I'm really already max'ing the 250W to over 289W, with the CPU, mobo, onboard gfx, DVD R/W+, 2-7200rpm SATA HDD. The SSD doesn't use much power. This is according to newegg's calculations here. Now, if I add a 90mm case fan ($4), it gets scary!
  4. Best answer
    foscooter said:
    To clearify:

    If I upgrade to a 650W PSU, will the 24-pin ATX power connector fry my mobo, as it only uses a 20-pin power connection from the 250W PSU now, even though it is a 24-pin connector on the mobo?


    Uhh... are you sure you're clarifying? Your statement suggests that you question if a 24-pin plug (connector) will fry your mobo. But your statement also suggests that your mobo uses a 20-pin socket ?(connection), coming from a 250 W PSU that has a 24-pin plug (connector).

    If you're asking what I think you are, then the scenario goes like this:

    The mobo is from an HP, which uses a 250 W PSU. This 250 W PSU has a 20-pin plug that connects to the mobo, which has a 20-pin socket. If you upgrade to the 650 W PSU that uses a 24-Pin plug, will it fry your mobo, which again, has only a 20-pin socket?

    If that is indeed what you're asking, then you'll be fine. The PSU 24-pin is backwards compatible to a 20-pin; the extra 4 pins can be disconnected from the 24-pin plug, leaving you with a 20-pin plug. As far as voltage and frying goes, the PSU will not push more current than the mobo needs. The PSU acts as a reservoir of power, in that you take what you need.
  5. No, you could have a 1000w PSU and it wouldn't fry your MOBO.
  6. Quote:
    The PSU 24-pin is backwards compatible to a 20-pin


    Thank You.

    Maybe I shoulda taken pictures.

    To re-clarify:

    Current set up: 250W PSU with only a 20-pin ATX power connector; Asus M2n68-LA mobo has a 24-pin connector. 20-pin plugs into 24-pin, and works.

    Upgrade: 650W PSU with 24-pin ATX connector; same mobo. Will the new PSU help or hinder the current mobo?
    Need it for SATA (current) and PCI-E connections (future). Current set up is already stressing the PSU.

    Sorry, just looked again: the 650W PSU has a 20+4 Motherboard connector. So it should work either way?
  7. Best answer selected by foscooter.
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