380Watts PSU enough for i7-4770 + R9 270?

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alexb75

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I have a 380 watts Seasonic, 80+ Gold PSU, 380 Watts, with 2 * 17A [34A] for +12 rail (combined 324 Watts), and would like to know if the +12 rail is sufficient to power this?

- Core i7-4770K [84 Watts]
- Asus mobo
- Asus R9 270 GPU (NOT 270X) [150 watts]
- 2 * 4GB DDR3
- 1 * SSD
- 2 * 5400RPM HDD
- 1 DVD, 1 Bluray
- 4 120mm fans
- 2 USB devices

I have looked at this site http:// and it tells me how much power I need, but not specifically how much power I need at +12 rail, which I believe is THE KEY spec.

Thanks
 
Solution
capt_taco



I wouldn't worry about this too much. In reality, almost all of the power drawn is going to be from the 12V rail, and 99% of the time if something gets overloaded, that's it.

So what I take that to mean is one of two things: each individual rail could handle the stated amount of...
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Newbbuilder11

Newbbuilder11

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I added up the wattage on some random specs that met what you have and it came up to about 333 watts, it will run it, but there might be power shutdowns while trying to game and that PSU will be on load almost all the time causing its lime span to dramatically decrease, I recommend getting a higher wattage PSU.
 
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alexb75

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Ok, why not? Like when I read reviews, the max wattage coming out of the wall is usually in 200s range, so how come we need so much power from PSU? Is n't it just CPU and GPU requiring +12V? and those two add-up to only 234 watts, at 80% efficiency on 324, I get to 260 which is still more than max need, no?

Thanks
 
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Newbbuilder11

Newbbuilder11

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You have to consider the RAM, mobo, HDD, SSD, fans, anything that you plug in take power, not just CPU and GPU. Since your PSU is rated to output only 380 watts, then your stuck, since you will be stressing your PSU with alot of load.
 
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Goodeggray

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The numbers for your psu are not adding up. It has 2 12V rails with 17A each so wattage from them is 2x12Vx17A = 408watts, and you still have wattage from the 5V and 3.3V rails. If the 12V rail info is correct the psu should be rated at least 450W. Watts is volts x amps. The wattage coming out of the wall outlets in the US is 1200 to 2400 watts. The voltage is 110v and most circuits are 10 to 20 amps.
 
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alexb75

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I agree, but that's what it says on the box! Could it be marketing and it's actually capable of a lot more? I remember when I bought it, I checked the 450 watts version and the detailed numbers were almost the same. Maybe 450 was 18A per channel...
 
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capt_taco

capt_taco

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I got 418W running it through the same calculator as you did, when you add in all the other components. Don't use this PSU for it.

And in fact, you probably want at least 500W to give yourself some breathing room (I'd go with 550Wfor that setup, personally). Ignoring efficiency for the moment, running your PSU at 75-80% of its rated capacity all the time is hard on it, and not the best idea in the long run. Granted, if you are only stressing it occasionally for gaming, you may not notice, but better safe than sorry, I say.
 
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alexb75

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So, here's the weird part... here's a pic of the box:
PIC OF BOX

But on their website, this is what they say for the model I have (380 watts), albeit my PSU is older and they may have changed specs on it...
Seasonic webpage

So, while both say, 324 Watts for +12V, the website says 27A combined, while my box says "17A * 2" which would be 34A, and that would fit it on their current rating between 430 and 520 watts! Quite strange...
 
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capt_taco

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I wouldn't worry about this too much. In reality, almost all of the power drawn is going to be from the 12V rail, and 99% of the time if something gets overloaded, that's it.

So what I take that to mean is one of two things: each individual rail could handle the stated amount of watts/amps, but if you go over 380 total, the unit will be overloaded. Or, 324W is the max on the 12V rail and they assume that the average person will start to bump into that when their total system is around 380W ... and even though the unit could handle 400 or 420W total, they know a good amount of that is going to be on 3.3V and 5V and is going to be unused, so 380W is their way of warning you to watch out. All of their units seem to be labeled that way, not just the 380W one.

You do occasionally hear stories of PSUs actually being able to handle more than their rated capacity in tests. Much more often, you hear about them blowing up far below it.

At any rate, bottom line, would I try to run that system off a 380W PSU? Hell no, for a bunch of reasons I explained.
 
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alexb75

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One follow-up... would a 760Watts PSU be overkill? The calculation says I need something around 450, now, I assume my idls is around 90-120 watts, and I believe the PSU 80-Gold are only efficient at 20% of power and more... so if I get a higher PSU, I potentially could be less efficient in idle and regular daily tasks, right?

What would be maximum PSU recommended here? I am looking into Seasonic X-series, that starts at 560 watts (albeit very hard to find), and the lowest available PSU is 660W...
 
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