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Questions regarding PSU

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April 21, 2014 11:04:31 AM

Do your best to answer all of it.

This is the power requirement of the current system I'm planning to get.

http://gyazo.com/6e6f0912a993a2da1fada02b49813171

71 - 309 (I'm assuming 71 is idle and 309 is under full load)

1) When getting a PSU do I get something that is at minimum 309+ watts or what's up?

2) I heard we were suppose to give some headway like 20% more than what you actually need is it correct? If the value is wrong feel free to correct it.

3) If I wanted to overclock how much more power do I need? Give me like a generalized amount like 25% more power or something? I'm not planning to overclock it just wanted to know for future reference.

4) Would it be bad to get a 550 watt PSU even though it's a overkill for the future cause I might add another GPU for Crossfire which will jump the power needed from 71-309 to 99-424.

More about : questions psu

a b K Overclocking
April 21, 2014 11:48:38 AM

With this build you will need a 450W Bronze certified PSU or 30A@+12V rail(which is more like a 500W psu). For Cross firing get a 550W like XFX 550W PRO Core edition 80+bronze certified.

Most power supplies are maximum efficient at 50% power load which also extends their life if operated at that load. For example for a system with 300W peak load consumption a 600W psu will provide max efficieny at load. But since system always doesnt operates at load a 500W psu is more favourable.

There should always be margin between peak power load of system and rated power output of psu. For a system with 300-325W peak load a good quality 500W psu is required.

There's nothing wrong in overkill . Since as explained most psu are more efficient at half load than their rated power output and also psu's tend to show decrease in power output with time so it is safer and better to get more in case of psu

Power consumption of an overclocked component depends on many factors. But for i5 4670k @ 4.6ghz power consumption is not above 100W at load.
http://www.bit-tech.net/hardware/2013/06/12/intel-core-...
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April 21, 2014 11:53:25 AM

* You want to get a power supply that can support all components running at max at the same time (a worst case scenario).
* Most of the high power parts use the +12v rails, so make sure the power supply provides plenty of power on the +12v rail (some ultra-cheap brands have a high wattage, but provide a lot less power on the important +12v rails).
* (#2) Only after you know the minimum you need to run max load, add extra padding so the power supply doesn't run at 100% capacity.
* (#4) Getting a higher wattage than you need is fine; the power supply still only consumes as much as it needs at any point in time ... the only downside is efficiency. Some power supplies are more efficient at certain power levels. Efficiency = the power loss (wasted power) when a power supply converts the power from AC to DC for computer use.

Here's a slightly different way to estimate power requirements:

Power for your computer:
4670K + motherboard & RAM & base system:
150W (AC)
http://www.xbitlabs.com/articles/cpu/display/core-i5-46...

R7 260X
93W (DC on +12v rail)
http://www.techpowerup.com/reviews/HIS/R9_260X_iPower_I...

So, add those two numbers:
maybe 250 as a minimum on the +12v rails.
350 to be safe.


So, you only need to find a power supply that gives you 350W on the +12v rails to run fine. Anything extra will just be for later.
For crossfire, you just add another 93W for the extra video card.... so 450W for Crossfire using all standard clock settings on all parts.
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April 21, 2014 4:40:00 PM

Okay I'm a bit lost from some of the articles I read online before asking questions here there was something about having enough watts but not enough of of the current you need. Like there's the +3.5v, +5v, +12v, -5v, and -12V. The one thing they really emphasis in that article was that even if you got a PSU with enough watt it might not provide enough +12v to supply your video card which will cause trouble for your system.

That being said how do I know what component takes the +v12?

So once I add up all the watts +12v components needs what do I do next because on the PSU I only see the A and not W next the the +v12?

For example the specs on a PSU says 115V ~ 230V +5V@25A, +3.3V@25A, +12V@50A, -12V@0.8A, +5VSB@3A which I'm totally not getting.

I'll keep reading more PSU articles to see if I can answer my own question while I wait for replies here.
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April 21, 2014 5:23:54 PM

This might help:
* Volts x Amps = watts
* In other words, 12v x amps = watts on +12v rail
* most high powered parts in your computer use the +12v rail (the video card is entirely +12v when running I think; the CPU is also +12v mostly, if not entirely).
* Since the two main high powered parts (CPU and GPU) used mostly the +12v rail, that is really all you need to focus on to get a general idea of the power supply is good enough.

So, in the example you gave:
+12V@50A
That's 600W or 50amps on the +12v rail... plenty for your needs.

Another example, based on the estimate I gave for the +12v rails:
350W or 29amps (350/12) is a pretty good amount for your CPU and GPU.
450W or 38amps (450/12) for Crossfire at stock speeds for all parts.
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a b K Overclocking
April 21, 2014 9:24:22 PM

AnimeFever said:
Okay I'm a bit lost from some of the articles I read online before asking questions here there was something about having enough watts but not enough of of the current you need. Like there's the +3.5v, +5v, +12v, -5v, and -12V. The one thing they really emphasis in that article was that even if you got a PSU with enough watt it might not provide enough +12v to supply your video card which will cause trouble for your system.

That being said how do I know what component takes the +v12?

So once I add up all the watts +12v components needs what do I do next because on the PSU I only see the A and not W next the the +v12?

For example the specs on a PSU says 115V ~ 230V +5V@25A, +3.3V@25A, +12V@50A, -12V@0.8A, +5VSB@3A which I'm totally not getting.

I'll keep reading more PSU articles to see if I can answer my own question while I wait for replies here.


The components that always require +12V are cpu , graphics card , cpu & case fans.
Hard drives require both +12V and +5V.
+5Vsb(Stanby) is required for turning on your pc
For calculating how much watts → Power(Watt)= Current ( Ampere) × Volts or P=V × I
360W=30A×12V
350W = 70A × 5V
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