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4850 only works without a dedicated power connection!

Discussion in 'AMD / ATI' started by rpb99, Oct 24, 2008.

  1. rpb99 New Member

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    Six weeks ago I bought a PowerColor HD 4850 PCS. I get endless freezes, crashes, restarts and BSODs in 3D games.

    Initially it was running on XP pro. More recently it is running on a fresh install of Vista. Same problems so I am assuming it is not a driver issue.

    I RMAd the card but the online store tested it, found it was OK and returned it - charging me £21 for the privilege!

    Temperatures seem OK – no higher than 70 degrees or so.

    My 2GB of Ballistix memory passed Memcheck, although I only had time for one run.

    I then started to look at the PSU. I have an old Antech 500 watt. I then tried two different PSUs, one 550 watt and the other a Jeantech Arctic 600 watt. Neither cured the problems (but admittedly they were not great PSUs).

    However, I hit upon a bizarre set up that does seem to cure the problems. The original 500 watt PSU is installed as normal, with a molex connection direct into the Asus A8N SLI Deluxe motherboard near the PCIe slot. However, the dedicated PCIe cable is NOT used.

    Instead, if you plug the Jeantech unit’s PCIe cable into the graphics card the problems seem to go away EVEN THOUGH THE JEANTECH UNIT IS NOT PLUGGED INTO THE MAINS.

    The 4850 must be getting all its power from the PCIe slot direct. If the dedicated PCIe cable is plugged into the card but not into the (disconnected) Jeantech PSU, the PC does not boot and instead asks for a cable to plugged into the graphics card. If the cable is then plugged into the Jeantech unit then, even though this is not plugged into the mains, the PC boots and the graphics problems do not seem to be present.

    I cannot run the machine with a brand new disconnected PSU sitting next to it so need to find out what all this means.

    I am thinking of swapping my single 4850 card to the second PCIe slot, although I am not sure if my motherboard will allow this.
  2. DrPepper

    DrPepper The Doctor is in the house

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    I dunno if this is a smart solution but try cutting off the connector and then using it :laugh: If anyone can think of something else go ahead mines seems kinda crazy.
  3. Grasshopper New Member

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    It sound like a PSU problem to me. Try the card with some more reliable PSU (600W at least).
  4. rpb99 New Member

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    I should have said that the Jeantech PSU is modular, so that it is possible to plug the PCIe cable into the 4850 but not the PSU - however if I do that the PC does not boot, saying that I need to connect a power cable
  5. DrPepper

    DrPepper The Doctor is in the house

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    thats wierd lol. I really can't think of why it does that maybe someone else will know but I think I've missed something.
  6. King Wookie

    King Wookie New Member

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    You shouldn't be able to run that card without power on that connector.

    I'm baffled for one.:wtf:
  7. Wile E

    Wile E Power User

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    Sounds like a power problem, when you describe the work around. Do you know anybody with a highr quality psu for you to test on?
  8. Widjaja

    Widjaja

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    I have no answers.
    But your situation is really wierd.
  9. SpookyWillow New Member

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    so with your "fix" are you able to run any games or anything?
  10. rpb99 New Member

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    Yes - it is very odd but games work better with my "fix" rather than with a powered dedicated PCIe cable. I can only assume that the card is getting its power through the PCIe slot direct, possibly courtesy of the molex connection into the motherboard.

    What baffles me is how two - admittedly cheap - new PSUs fail to solve the problem, one at 580 watts and one at 600 watts.
  11. SpookyWillow New Member

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    its not so much the wattage but how many amps on the rails, even then cheaper PSU makers tend to be very generous with what they tell you.
  12. rpb99 New Member

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    The Jeantech unit had 19 amps on the two 12 v rails. I have never understood how you can be sure these are being combined in the PCIe cable

    Here is the spec

    http://jeantech.com/600.htm
  13. rpb99 New Member

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    OK - so I ended up buying an OFG 800 watt PSU for £129 but the PC kept crashing!

    Eventually by much trial and error I have established that what keeps the system happiest is for the 4850 to be underclocked to a maximum of 900 / 600

    Why this should be I do not know. As I have said, I tried to RMA the card with Overclockers UK but they tested it and reported it OK, charging me £21 for the privilege.

    It is not much of an underclock but is a bit galling, especially when the card (Powercolor) comes factory overclocked and the whole process has cost me one fried hard drive (my fault!) one reinstall, three returned PSUs and much wasted time and effort.
  14. insider Guest

    If you have to underclock then the card is faulty, I'm not surprised at overclockers UK action, they are bloody thieves, avoid them like the plague next time!
  15. MopeyMartian

    MopeyMartian New Member

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    This is just a shot in the dark...

    ATITrayTools allows some voltage adjustment of the GPU. Maybe you could turn the juice down a little and see what happens.
  16. tigger

    tigger I'm the only one

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    Try getting in touch with trading standards in the uk,also make a video showing your problem and try sending it to overclockers.If you still get no joy,i'm sure trading standards can order overclockers to replace/refund the card.
  17. EviLZeD

    EviLZeD New Member

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    this is why i dont buy from them anymore unlucky man
  18. niko084

    niko084

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    That's some BS, you have a faulty card... They probably plug it in and say look computer shows post.. It's good.
  19. rpb99 New Member

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    They reckon to have run Crysis and 3dmark 2006 for a couple of hours.

    I suppose that if my system is quite old (a few years) and has slightly dodgy RAM, MB or PSU then the 4850 might work fine on a new super duper system but not on mine.

    I really do not like the prospect of more wasted time arguing with overclockers and will probably live with a small underclock.
  20. kajson

    kajson

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    The only thing that sounds plausible to me, is that all your PSU's are maybe have 2 12V rails and when you do plug all the power in, the pci-e slot isnt able anymore to provide the 75watt on a stable basis?

    Maybe your mobo could have some issues? Try looking if there's an upgraded bios or something, and is your system OC'd in any way?
  21. niko084

    niko084

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    Now that I think about it, almost sounds like maybe the pci-e plug is shorting out or supplying the wrong voltage at the wrong location maybe.. Either card or adapter level...
  22. Polarman

    Polarman New Member

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    My K9A Platinum has such a molex connector near the PCIe and that's plugged in. My 4870 has both it's 6 pins connectors plugged in has well. I do not have any issues.

    Note that the PSU i use has a 60amp single rail.
  23. titan New Member

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    Unplug the motherboard molex(EZ-PLUG), and plug that lead into the gfx ONLY. Don't reconnect the EZ-Plug. Still get the problem?

    If that lead has multiple connectors on it, does anything else hang off it?
    Last edited: Nov 3, 2008
  24. spearman914

    spearman914 New Member

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    In that case you can try a different PCI-E connector. ;)

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