what PSU do i need for my build?

25th of February 2014 2

what PSU do i need for my build?

Question by james: what PSU do i need for my build?
saphire radeon hd 7770 GHz edition DDR5 1 GB $ 110


AMD fx-4300 3.8GHz 4.0GHz turbo $ 120


LITE-ON DVD Burner $ 15


COOLER MASTER Storm Enforcer ATX mid tower $ 80


G-Skill 2x4gb RAM DDR3 1600 dual-channel $ 55


ASRock 990FX Extreme3 AM3+ AMD 990FX SATA 6Gb/s USB 3.0 ATX AMD Motherboard with UEFI BIOS $ 120


seagate barracuda 320GB 7200 RPM SATA 6gb/ps $ 60


Hanns-g 21.5 monitor full hd 1920×1080 $ 100


Microsoft Windows 7 Home Premium 64-bit $ 100


people have told me “450 watt minimum” to “you’ll want at least 800 watts”
that is a big price range so please tell me who is right

Best answer:

Answer by Albert W
Hi There,

According to the link below at Tiger Direct the video card needs a minimum of 600 watts.

The rest of the components should need somewhere under 200 watts.

I would opt for the 800 or 850 watt power supply.

If the PS is low the video card can cause system crashes under high loading.
Another thing is low power can really shorthen the life of the hard drive.

Hope this helps,

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2 great comment(s) for this post

  1. doruletz1999 7:36 pm 25/02 of 2014

    Your RAM is So-Dimm (for laptops), it will not fit or work in a desktop PC, buy desktop RAM:

    Don’t listen to “Albert W”
    When AMD says 500W they take in account all other components, not just the card, which by the way only draws under 75W of actual power for itself.

    For GHz edition HD 7770 AMD recommends a 500W (or greater) power supply with one 75W 6-pin PCI Express power connector

    You can never have too much power, your system will only draw what it needs.
    Get at least a 600W.

    Power supplies will lose power output in time due to capacitor aging, also it is never a good thing to stretch a power supply to its maximum output. You only get higher temperatures inside your box and noise from the screaming PSU fan.
    It is best to use a power supply at least 100W bigger than what your graphics card manufacturer recommends for minimum power.
    Example: Get at least a 600W if nVidia or AMD says you need a 500W or bigger power supply.
    Also you must match the PCI-e card power cable requirements for you card. Example: two 75W 6pin or one 75W 6pin and one 150W 8pin, etc.

    For your actual system power needs, use a power calculator such as one of those bellow:

    Fill in all that apply for your system, choose 50% capacitor aging to account for future wear and tear, and hit calculate.
    Add 30% or more to the calculated value, for lower running temperatures, less fan noise, and to allow for some future upgrades.
    That’s how big of a power supply you need.

    Cheap, no name, generic power supplies tend to grossly overstate their power output and they can spike or crap out and fry your key components.

    Only buy a reliable brand name like Corsair, Thermaltake, Cooler Master, Enermax, Antec, XFX, Seasonic, OCZ, or Silverstone.
    Make sure it’s an 80 plus certified power supply (80 plus means guaranteed over 80% of rated power in actual output)
    It is also preferable to get a modular power supply, to eliminate cable clutter and allow for better air flow in your box.
    NEVER CHEAP OUT ON YOUR POWER SUPPLY, it’s the engine that drives your entire computer.

    Good luck with your build

  2. featherawr 8:03 pm 25/02 of 2014

    There aren’t very many guides to learning what PSU to get, how much power you need, how much you’ll use etc, so I’ll explain the basics:

    When it comes to power supplies you really only need to look at the 12v rail, which is how much 12v power it can output. Almost all of the major components that use a lot of power use 12v power, such as the CPU, video card, HDD, etc. Your RAM and board components use like barely anything so you really don’t need to worry about them as all power supplies have PLENTY of power on the 3.3v and 5v rails, unless I guess you plug in like 30 optical drives you’re good.

    So now you might be asking, well that’s all nice and dandy but how can I actually find how much power my PSU can output on it’s 12v rail? Well, the way I do this is by Googling the component followed by Newegg, such as “XFX 450W Newegg”. After that I click on Newegg’s product page and then open up the product images; from here Newegg will ALWAYS have pictures of the PSU label which will have the amperages of it’s respective rails. You can convert the amperage to wattage by multiplying the voltage and amperage, so:
    “V * A = W”.

    With that being said, I found out how much power all your components should use along with sources to where I found it; they should help you a little bit. ;)

    Stock HD 7770 (Guru3D review):
    = 86W

    Stock FX-4300 (Newegg product description): http://www.newegg.com/Product/Product.aspx?Item=N82E16819113287
    = 95W (not all of this is 12v but most of it is, I don’t think you can really even find the exact 12v power consumption so lets just go with 95W k)

    LITE-ON IHAS124-04B (Google the model #): http://www.dimaco.com.mx/imagenes/LITE-ON%20IHAS124_04%20B_CLOGO.jpg
    =2.5A * 12v = 30W

    Seagate 320GB (Newegg product image of the label): http://www.newegg.com/Product/Product.aspx?Item=N82E16822148766
    =0.52A * 12v = 6.24W

    Total = <217W

    So now you're probably thinking, what the hell that's really low??!! I'll explain, when AMD states you need a 400W power supply as a minimum requirement they're meaning that you should be using a PSU that is marketed as a "400W" power supply. So basically they're recommending something like a Corsair 430W, XFX 450W, something around those lines. Something I really want to stress as well is that the minimum requirement is NOT just for the video card, it is for the ENTIRE system.

    Anyway, now the question really is, why would they recommend a PSU that can power double what it actually needs? The reason is because PSU's are most power efficient at around 50-60% load, will be more reliable and are much less at risk of overloading the rails and blowing the power supply. Remember here, the people making up the minimum wattage don't want people RMA'ing their hardware because it exploded their power supply, killing their entire computer; that's not a very good business strategy. Generally speaking, as long as the PSU is from a legit company, as long as it has the necessary PCI-e connectors for the video cards it's probably a perfect match.

    Kind of the reason why you see people sometimes recommending 800-1000W power supplies when you really could run it on a 250W piece of crap (but don't, lol) is that they end up adding more power, multiplying things for no reason, etc, it's kind of ridiculous sometimes.

    Like they'll be like, okay 400W for the video card, 200W for the rest (which isn't even right), now we're at 600W, now we need another 50% so the PSU runs at 50-60% efficiency (WHICH IT ALREADY WAS AT 400W!) so now we need a 1200W, and then they'll be like hey lets just add another 20% for capacitor aging (which should be like 10% tops, it's not like you'll use the same PSU for 5+ years). So now we're at 1500W. gg wallet, gg

    See how easy it is to get from 200W to 1500W using stupid logic? This is kind of an extreme case though, but I've actually seen someone say this so yeah; this here is full retard.

    Okay I guess that wasn't just the "basics", but w/e, maybe I'll make TL;DR:
    * GET A CX430 for $ 19 after MIR! http://www.newegg.com/Product/Product.aspx?Item=N82E16817139026&Tpk=cx430&IsVirtualParent=1
    Even if you did read all that I guess you should read that too.

    And yeah you shouldn’t get the SODIMMs, like it says laptop memory. I’d strongly recommend trying out http://www.pcpartpicker.com/ it checks compatibility, etc manually so you won’t end up with RAM that doesn’t fit in your board. :)

    btw the reason the HD 7770 can draw beyond 75W is because the PCI-e slot can pull 75W from the board and the PCI-e 6-pin can pull another 75W, adding to a total of 150W. Lol we seem to have made ourselves a wall of text here, lololol.


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