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Mod 4-pin molex to 12v P4 plug?

Discussion in 'General Hardware' started by Doohickey, 13 Jul 2006.

  1. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    I have an old non-P4 PSU I want to stick in an old P4 system, but have the problem that I haven't got the right plug for the 12v CPU plug.

    Right, so I found this on a certain auction website:

    [​IMG]

    Which looks like it solves the plug problem, but will I still need to mod the molex to output 12v or will I just be able to plug in and go? I'm not very clued up on voltages etc...

    Any help appreciated :)
     
  2. Corasik

    Soldato

    Joined: 5 Jan 2003

    Posts: 5,002

    Location: West Midlands

    The molex will have 12V anyway, so just plug and play. Just one thing worth mentioning, the ATX+12 is designed to deliver 12amps of power to the processor, a Molex only has 1 cable for 12V, and shouldnt really be loaded much higher than 6amps.

    However most motherboards seem to split the draw of 12v between the ATX cable and the +12 cable. So as long as your not running a dual core PentiumD @ 4.1Ghz then it should be fine.
     
  3. AndyOcUK

    Mobster

    Joined: 15 Feb 2006

    Posts: 3,432

    Location: Staffordshire

    Unless your PSU is a quality one (e.g. tagan, seasonic etc) this will cause problems if your CD/DVD drives, HDDs and case fans etc are sharing the same Rail.

    On a truly suitable PSU for this board, the CPU will have this plug on a dedicated rail.

    Regards

    AndyOCuK
    OCuK Tech Dept
     
  4. Corasik

    Soldato

    Joined: 5 Jan 2003

    Posts: 5,002

    Location: West Midlands

    Yeah, check the label on the side of the PSU, and see how many amps it has on its 12v rail.
     
  5. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    Thanks for your replies guys :)

    Corasik:

    The label on the side of the psu says:

    +12v = 8.0A (YEL)
    -12v = 0.8A (BROWN)

    I have no idea if that's good or bad lol. It'll be running a P4 2.6 Northwood with no overclocking plans.
     
  6. Corasik

    Soldato

    Joined: 5 Jan 2003

    Posts: 5,002

    Location: West Midlands

    8A, thats VERY low for +12V, thats an old school PSU from when the CPU's were running off the 5V rails. You've only got 96W to play with there, and a 2.6 Northwood can use (guessing here) around 65W on its own. Now if you have a 'low end' graphics card then that can power off AGP and it will draw from the 3.3V or even 5V rail, so that would help, but it wont leave you much power for hard disks.

    A single hard disk, and 1 optical drive and you 'might' be ok on it. But if you do decide to use that PSU, be very carefull not to be tempted to stuff in alot of extras.

    Oh yeah, the motherboard will draw a little 12V as well.

    Dont even consider it if the graphics card has a molex for additional power, even an older card like an Nvidia FX5800 series would draw enough 12v power to take you well over the 8amps limit.

    I was hoping you would have 12amps or more on the psu. 8amps could work, but be very carefull, and dont be tempted to throw in any powerfull hardware without upgrading the PSU.
     
  7. jellybeard999

    Sgarrista

    Joined: 7 Feb 2004

    Posts: 7,784

    Location: NE

    i couldnt run a xp1800 and cheap mobo with a dvd-rom on a psu @ 12a 12v rail... doubt it'll even boot tbh... the boot up surge will be too high
     
  8. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    Heh, I should really have said what it'll be running in the original post :p

    I was going to try and power:

    P4 2.6 Northwood
    Radeon 9600XT (seems to be powered off AGP)
    56k PCI modem
    1x DVD drive
    1x HDD

    That's literally it, it's meant to be a backup computer, not going to be used that often.

    A bit too risky?
     
  9. AndyOcUK

    Mobster

    Joined: 15 Feb 2006

    Posts: 3,432

    Location: Staffordshire

    MIGHT JUST be OK. Just to give you an idea to compare, any half decent PSU (E.G. Tagan 580W U15) will have TWO 12V rails each apable of at least 18A each and on the Tagan they can be combined to make on FAT 38A 12V rail. To be fair, this is a certified SLi PSU and these stats are required to power two cards in SLi but its a good indication of the demands a modern system places on a PSU.

    If your post is an absolute list of everything in the system then you should be OK but ONLY IF you make absolutely sure that the cable you apply the converter to is coming straight out of the PSU and is not shared by any other devices such as CD ROMs and ESPECIALLY Hard Disk Drives.

    By the way, we stock these converters.

    Best Regards

    AndyOcUK
    OcUK Tech Dept
     
    Last edited: 15 Jul 2006
  10. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    Thanks for the reply Andy :)

    Yep that list was everything in the system, nothing more.

    Are you sure you stock those converters? I was in the shop on Thursday and asked at the desk and the guy said that you didn't sell them, and I checked at a certain competitor and they don't have them in either. :confused:

    If you did stock them that would be great, as I will be popping in again on Monday I think to pick something else up as well :)
     
  11. AndyOcUK

    Mobster

    Joined: 15 Feb 2006

    Posts: 3,432

    Location: Staffordshire

    Hi again

    I'm the technical manager at OcUK. I've checked and these are not on the website but I have a drawer full in the dept. Ask for me and I'll dig you one out. It'll be about £2.50 ish.

    See you Monday. ;)

    AndyOcUK
    OcUK Tech Dept. :cool:
     
  12. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    Thanks Andy :)
     
  13. AndyOcUK

    Mobster

    Joined: 15 Feb 2006

    Posts: 3,432

    Location: Staffordshire

    Hi,

    You got it working OK? :)

    AndyOcIK
    OcUK Tech
     
  14. Doohickey

    Sgarrista

    Joined: 8 Aug 2004

    Posts: 9,341

    Location: Shropshire

    Yup, seems to be working just fine, and a lot cooler and quieter than when I remember last using the psu, which is a nice surprise!

    Thanks very much again :)
     
  15. AndyOcUK

    Mobster

    Joined: 15 Feb 2006

    Posts: 3,432

    Location: Staffordshire

    No worries