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Understanding PSU requirements

Discussion in 'Newbie Lounge' started by amanbra, May 22, 2018.

  1. amanbra

    amanbra Member

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    Hi Everyone,

    First post here,

    I have a nice small gaming rig in a 250D that finds nicely into a Ikea cube bookshelf.

    7600k @ 4.7
    Initially started the system with a 1060 6gb but upgraded to a 1080ti ASUS Turbo when I got the x34p monitor.

    I have a RM550x PSU. I got a bit worried that the psu was too low with other forums/websites telling me i needed 600 - 650+... The Coolermaster site recommended a 750w...

    I got a watt meter from Jaycar and looked at the power draw. When playing Pubg it pulled about 340w from the wall. To max out the system I ran prime95 whilst in PUBG and pulled about 375w from the wall.

    Is this the right way to test power usage or am I missing something critical that can also put a lot more load on the PSU and potentially get myself in trouble?

    Secondly, I might grab myself a 8 core cpu at some point as money might be short after a new bub comes along and I need to get my stuff purchased before hand. Based on my testing above I have about 200watt headroom, so is it correct for me to conclude that the 550w psu is fine for the new 8 core coffeelake or 2700x?

    There will be mild overclocking to the point the U9S cooler can cope.

    Thanks in advance guys
     
    Last edited: May 22, 2018
  2. adamsleath

    adamsleath Member

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    Last edited: May 22, 2018
  3. OP
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    amanbra

    amanbra Member

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    There is so much out there that suggests that 750 is total overkill. Surely momentary spikes are not going to hit 650 - 700 watts?

    For the ideal load on the PSU being 50% is that actually proven anywhere? I know there are efficiency curves out there but we're generally talking 1% efficiency variance between 30% to 80% load.

    the RM series from corsiar has some of the lowest ripple out there and i quite like the brand so will be sticking with them. Just wondering if there is a way to assertain if the 550w is actually enough.
     
  4. adamsleath

    adamsleath Member

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    yes it's overkill.

    the power meter is the sure way. stick with the 550W. point is if you are getting a new psu...not much money difference particularly if you have a 10 year warranty. the 550W may clap out before then. it does happen.

    most of these systems i doubt you'd need to go above 650W psu unless you had 2 graphics cards...
     
    Last edited: May 22, 2018
  5. OP
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    amanbra

    amanbra Member

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    yeah if i were building now from scratch and I knew i was going to run an 8 core cpu with a 1080ti I definitely would have gone a RM650i or similar.

    Just wondering if the 550w is actually ok though as I do'nt want to have to replace it, it was a 150 dollar unit a year ago...

    Thanks for your thoughts.
     
    Last edited: May 22, 2018
  6. adamsleath

    adamsleath Member

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    Last edited: May 22, 2018
  7. MR CHILLED

    MR CHILLED D'oh!

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    Surely better to have some breathing space rather than risk going too low just to save a little bit of cash. After all it is the life blood of your system.
     
  8. miicah

    miicah Member

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    PSUs run more efficiently at certain load %'s, and you aren't going to get draw spikes up to twice the load in a game.
     
  9. HobartTas

    HobartTas Member

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    Hard drives that use high single digits in watts when in use can pull 20-25 watts when starting up so this is an issue when you have a dozen of them in your case but otherwise yes your right there aren't any large momentary spikes involved for anything else you use other than perhaps a heavily overclocked and overvolted CPU. You also have to check what manufacturers mean by the power rating and for some a 550 watt power supply is maximum peak power whereas for say Antec they mean you can draw 550 watts on a continuous basis.

    The main reason to pay a bit extra and get an oversized 750 W power supply for a 375 W load is usually the PS fan can be noisy and typically doesn't spin up at all until the load hits 50% which in this example means it would still be idle. I was looking at getting an Antec High Current Gamer 850 W but the review for the power supply was great for almost everything except for the noisy fan so I got the even more expensive High current Platinum Pro 850 instead for my 4930K and GTX1070's in SLI.
     
  10. Smokin Whale

    Smokin Whale Member

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    550w is perfect, no need to upgrade. Hell I run an i7 2600 and a GTX 1060 off a 300w Bronze rated OEM PSU (FSP) and it's fine, never had an issue. Also have an i5 2500 + GTX 1050Ti (OC) running off a 220w OEM PSU without issues.

    Also, "load spikes" are the biggest load of nonsense I've heard all day, it's not as if computer hardware randomly transforms itself into something more power hungry for lulz. If you run a set of synthetic benchmarks (eg. Prime95 + Furmark simultaneously, or OCCT PSU Test) you should be able to instantly and consistently determine the maximum power draw. If it's less than 90% of the PSU's total load (in particular, 12v rail load), then there is nothing to worry about.

    Edit: Coffee Lake CPUs consume slightly more when overclocked, but nothing significant. They are more efficient per clock, but they just have a couple of extra cores.

    Edit Edit: Power draw values from the wall don't take into account efficiency variables. If you have a PSU that is 85% efficient at 40-60% load, and you are drawing 200w from the wall, then actual power draw is around 170w on the PSU.
     
    Last edited: May 25, 2018
    miicah likes this.
  11. adamsleath

    adamsleath Member

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  12. MR CHILLED

    MR CHILLED D'oh!

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    And what of purchasing extra for future requirements?
     
  13. miicah

    miicah Member

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    More than likely a future upgrade will be more efficient so your power requirements will actually go down.
     
  14. adamsleath

    adamsleath Member

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    the unknown factor to me is quality and longevity of the psu's internal components. i overkill it to get higher rated components running under less stress.
    https://www.pccasegear.com/products/41817/seasonic-focus-plus-gold-750w-power-supply
    ive fixed onto this one for the moment - there are probably better/comparable for the money psu's always interested to hear comments though. psu fetish seasonic :D
    perhaps they are getting better and better across the board.

    reliability and longevity is the aim..depends how long you want it to last.

    whether it was a 400w (maybe the fanless 400w seasonic platinum has better grade components? dunno enough about the design of psu's to recognise the build quality) or higher id still be looking at reviews to find the best performance and the 10 yr warranty. thats money you dont have to spend for 10 years on the psu any way you look at it.

    i have two other psus i replaced because they are old, but ive tested them and they still work. antec sg850 (10yrs old) and a corsair hx850 (7 yrs). they werent cheap though
     
    Last edited: May 27, 2018
  15. OP
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    amanbra

    amanbra Member

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    I have an ITX build so to be honest other than adding more HDDs there really isn't much more opportunity to expand.

    the RM550x unit from corsair has stellar reviews as far as i'm concerned is a top shelf unit. In saying that i'm fairly certain i won't be using it more than 5 years as i'm likely to refresh everything at that point...

    I'm just worried i've missed something in my power testing and i could do something to cause a meltdown..
     
    Last edited: May 29, 2018
  16. adamsleath

    adamsleath Member

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    does it get loud or is it running particularly hot? if not i wouldnt worry. one of the reasons i went to a higher spec unit was for a quiet fan and cooler operation (both related to each other) but 10 years ago there tended to be less well designed psu's aswell. i think the 550 is a sensible option based on your actual power draw.

    the original corsair hx620 was a big thing when it came out (12 yrs ago). ive still got it. havent tested it recently though....
    im tempted to give it a bash. maybe on a el cheapo 2nd hand build...considering its age :lol:
    --
    the highest draw ive seen on a system that ive run just got over the 500W line of power draw. (from memory) mostly it sat in the high 300W range 380 to 450W ish from the wall playing games. these were sli and cf systems one was 8800gts sli and the other 5870CF. my power meter (actually probably exactly the same jaycar one they are still selling) no longer works. i replaced the battery. it's just kaput.

    the 620W was considered adequate for sli...but i went higher for some reason. worry? noise heat? cant remember.

    quite a few people on forums opted for a 750W for sli systems i remember.
    i also had an x750W seasonic but i sold it. too many psu's ! :lol: wish id kept it now for the collection :D
     
    Last edited: May 29, 2018
  17. OP
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    amanbra

    amanbra Member

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    Yeah so after the 1080ti install the psu fan ran for the first time =) as it has a passive fan mode. It's a 18dba fan so no i can't hear it but further to this the damn blower style gpu is fairly loud... as everyone knows...
     
  18. terrastrife

    terrastrife Member

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    Drawing 375W from the wall so you're using maybe 350W. To give you perspective, my CPU draws 160W at full load (overclocked Intel 6 core), and a GTX 1080Ti is 250W, and I peak around 450W PSU output. Buying overkill PSUs put you outside the peak efficiency curve, not that it really matters. I deliberately went with a 1000W PSU that doesn't turn the fan on until over 450W to keep it silent, however, the system has run on a Silverstone 450W in the past.
     
  19. adamsleath

    adamsleath Member

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    do you have peak power draw figure reading by your meter?
     
  20. MR CHILLED

    MR CHILLED D'oh!

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    lol....ok I give in :p
     

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