Trouble powering a gtx 970

Discussion in 'General Hardware' started by Halloween Jack, Feb 19, 2017.

  1. Halloween Jack

    Halloween Jack Maha Guru

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    Hi guys,

    My son has a budget PC cobbled together from some old parts and a few low cost purchases.

    He's got a very old PSU of mine (14 years old?), an Enermax 470W with molex connectors.

    He also has:

    H81M-P33
    Pentium Anniversary G3258
    GTX 750 Ti
    Crucial Ballistix Sport 8GB

    The 750Ti is powered by a adapter lead that uses 2 molex to a standard 6 pin.

    We wanted to see how my MSI 970 would work in there as an upgrade.

    This requires a 8 pin and a 6 pin. I had a couple of leads that converted 2 molex to 6 pin, then 6 pin to 8 pin so we tried that.

    It all started ok, with its fans running, but after boot up the fans stop and any game he tried was very laggy.

    I would have thought 470W would have been enough.

    Maybe it's something to do with how I connected it?

    Anyone know what was wrong and is it possible to get it working as things are?

    Cheers
     
  2. The Goose

    The Goose Ancient Guru

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    Just put your psu in your kids pc and get yourself a new one...or treat your son to a new one....14 years, time to put it to rest.
     
  3. Halloween Jack

    Halloween Jack Maha Guru

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    Thanks for your response.

    I could tell him he'll have to buy say, an EVGA 500W £33, but I'd like to tell him he definitely has to and know why it doesn't work.

    Even £33 uses up most of the rest of his Christmas money :(

    Any idea why it's not working?

    Cheers
     
  4. Wolf9an9

    Wolf9an9 Member Guru

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    The 470W rating on it's own does not mean much. You need to look at how many Amps the +12V is rated at.

    Your GTX970 (without other overclocking software) is designed to have it's fans off below 60 degrees C.

    Also the G3258 dual core without hyperthreading may be too low end to handle the GTX 970 which is still a fairly high performance card.
     

  5. Halloween Jack

    Halloween Jack Maha Guru

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    They have different rails don't they? I don't know much about it.

    But I imagine each rail has a different Voltage and Amperage.

    I'll look into this.

    I thought the fans might be off below a certain temp, that's why I got him to try it in a game but they didn't start.

    I thought it would be a bottleneck with that CPU. He'd be looking to upgrade that in June perhaps.

    But do you mean the CPU can't actually run the card properly?

    Cheers
     
  6. Halloween Jack

    Halloween Jack Maha Guru

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  7. Wolf9an9

    Wolf9an9 Member Guru

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    The P/S will have a printed label with all it's different Voltage rails and the Amps each rail can handle shown. (i.e., +12V, +5V, +3.3V etc.)
    Look at whether it has a single +12V rail (most likely) and how many Amps it is rated at. Here you should be looking for at least 30Amps.

    Had a quick look online and not sure I looked at the correct model but seems you may have two +12V rails rated at 15A and 16A. This may just be sufficient to power the 970 provided you make sure that the 6 Pin is powered from the 15A rail and the 8 Pin from the other 16A rail.

    Yes I mean the CPU is probably not up to the job and bottlenecking the GPU.
    You could try downclocking the 970 quite a lot and see if the games become smoother to confirm this.

    Also I am assuming that you have a proper Nvidia graphics driver for the GTX970 installed?
     
  8. Wolf9an9

    Wolf9an9 Member Guru

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    Don't understand question (how come it's not 460/12+38.3?)

    If you only have a single +12V rail then all Molex connectors are connected to it.
    However make sure that the two connecters to the 970 are connected to different molex connecter cables coming out of the P/S to spread the current (Amps) running through them.
     
    Last edited: Feb 19, 2017
  9. Halloween Jack

    Halloween Jack Maha Guru

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    Thanks for your help on this.

    It's a single 12V 33Amp rail.

    You didn't understand my question as I typoed a + instead of an =

    I meant that I thought you divided the Wattage by the Volts to get Amps.

    ie 460W / 12V gives 38.3A. I'm curious to learn about all this as I know next to nothing. That was something I read while googling this situation.


    So the 12V rail is on more than one cable from the PSU? I thought different cables had different rails.

    It looked as if nearly all the cables had molex connectors on them.

    Also, any idea what I should downclock the 970 to? like roughly?

    Thanks
     
  10. Wolf9an9

    Wolf9an9 Member Guru

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    Yes V x A = W therefore the max Wattage for the 12V rail is 396W. The difference between this and the 470W is made up by the other 5V, 3.3V etc. rails. However if you multiply all the other rails V x A and add them to the 12V wattage of 396 you actually get a much higher Wattage than 470. This is because all the rails cannot all deliver their max rated current at the same time and the averaged max wattage is limited to 470W.

    Your CPU also uses a fair amount of Amps from the same +12V rail. All the yellow wires are + 12Volts.
    So yes, the 12V rail is on more than one cable from the PSU.

    I would suggest downclocking to about half of the speed or about 600 Mhz

    Also can you mention which games are lagging ? i.e. are they high graphics demanding games?
     
    Last edited: Feb 19, 2017

  11. Halloween Jack

    Halloween Jack Maha Guru

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    Thanks for explaining that.

    Very good to know.

    One last, maybe stupid question...

    If I down clock to 600Mhz won't that be less than the 750Ti (at about 1000Mhz I think) and so actually be a downgrade? or is it better because of cores and RAM?

    Will it actually be an improvement over his old card.

    Thanks
     
  12. Wolf9an9

    Wolf9an9 Member Guru

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    The downclocked performance may be roughly equivalent to that of the 750Ti but the purpose of downclocking is to confirm that if the game now runs smoothly that the cpu is bottlenecking the graphics card at it's normal speed.
     
  13. Halloween Jack

    Halloween Jack Maha Guru

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    Right I see.

    It's definitely worth checking and I might get more out of it.

    Thanks for all that mate :)
     
  14. Wolf9an9

    Wolf9an9 Member Guru

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    It's a pleasure. Let us know how it goes.

    For info, a PC that I built for my grandson years ago had a core 2 Duo at 3.5Ghz and when I replaced the original 8800GTS with a GTX 295 the CPU could not handle it without downclocking the GTX 295 a lot. The PC also had a good 800W PSU
     
  15. Halloween Jack

    Halloween Jack Maha Guru

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    Ah good to know.

    He's bought an SSD so we're going to install that first - makes everything so much zippier, it takes an age to boot up at the mo'

    Once that's done we'll look into the gfx card.

    Thanks again.
     

  16. Harper

    Harper Guest

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    after 14 year i doubt that psu will be performing anywhere near 470w tbh.
     
  17. Agent-A01

    Agent-A01 Ancient Guru

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    Buy a PSU man, don't try to save a nickel either.

    I can't fathom why one would try to run a 14 year old PSU on newer hardware.
    You're just asking for issues/damage to hardware.

    Even new 500w $40 crap PSUs would be better than that enermax and i wouldn't even risk plugging those into the wall.

    Replace that junk and stop trying to bandaid solution by downlocking a 970 by half.. :puke2:
     
    Last edited: Feb 24, 2017

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