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How many watts i need in a new power supply ?

Last response: in Components
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June 10, 2012 8:14:48 AM

Hey,
i want to buy a RADEON HD6850.
now i have:
intel core i3 540 3.07Ghz
hp-d3006a0 300W (power supply)
MSI 2A9Ch (motherboard)
SAMSUNG T220P 1920X1200 monitor
and the current video card is ATI Radeon HD5450

now, if i will buy the HD6850, which power supply will I have to buy ?

More about : watts power supply

a c 110 ) Power supply
June 10, 2012 8:18:58 AM

At least a quality 400W.
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a b ) Power supply
June 10, 2012 8:37:46 AM

400W would be a minimum. 500Watt would be a more comfortable fit.
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June 10, 2012 11:12:31 AM

thanks.. more opinions ?
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a c 243 ) Power supply
June 10, 2012 11:18:44 AM

abekl said:
400W would be a minimum. 500Watt would be a more comfortable fit.

More comfortable in what way ?
The I3-540 uses slightly less power than an I3-2100
Toms June 2011 build with an I3-2100 and a HD6850 wouldn't put a 50% load on a 380 watt psu when stressed with Prime and Furmark

http://www.tomshardware.com/reviews/diy-gaming-pc,2970-...
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a c 158 ) Power supply
June 10, 2012 12:54:31 PM

+1 with Dell
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June 10, 2012 1:42:36 PM

so 430W will be enough ? cause i heard that even 500W wouldn't be enough..
and can you please explain your answer so i'll know for the future ? :) 
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a c 243 ) Power supply
June 10, 2012 1:47:22 PM

Pokeliz said:
so 430W will be enough ? cause i heard that even 500W wouldn't be enough..
and can you please explain your answer so i'll know for the future ? :) 

430 watts would be plenty, usually harder to find them with the dual 6 pin connectors that you may need, depending on the 6850 you're using, but they are out there.
It's about power consumption, and, as pointed out in the Toms build article, your system just doesn't require a whole lot
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June 10, 2012 2:05:19 PM

Dont' look at the watts, look at the amps on the 12v rail. 30 to 40 amps should be about right. Anything less than that, stay away.
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a b ) Power supply
June 10, 2012 2:15:30 PM

Pokeliz said:
so 430W will be enough ?

Single-GPU systems typically fall in the 150-250W range, 300W with the most power-hungry single-GPU cards.

The i3 and 6850 are by no means the most power-hungry components on the market, even a true 300W PSU would be enough. The reason why there are so many over-inflated power figures is because too many PSUs fail to meet their ratings even fresh out-of-the-box and even more will fail prematurely at high loads, which effectively means they were not designed to provide what they were rated for.
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a b ) Power supply
June 10, 2012 3:22:33 PM

When people talk about quality PSU's, they mean PSU's mainly that can output stable and accurate Voltage on all rails as well as supply appropriate amounts of current. Take two power supplies, both output 500watts according to advertisement. One power supply gets this power by providing tons of current at just 3.3V while the other outputs tons of current at 12V. Remember, current is a lot harder to produce at higher voltages...it requires better components. As the 12V rail is considered very important, make sure you have ample current at this rail. If you have a 1000watt psu but just ten amps on your 12V...it wont handle a damn thing. So watts ARE important, but only tell you half the story. For example, a corsair AX650 is advertised at 650watts, but it outputs 648 at just the 12V rail alone...! Thats what you need to know. After that just add numbers up.
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June 10, 2012 5:09:58 PM

http://www.graphicscardbenchmarks.com/index.cfm?page=sp...
This shows how much a lot of the cards use. Just divide it by 12 to find out how many amps you need.
There are a couple of mistakes in it (GTX 670 does not use anywhere near 349 watts) but most are correct.
You should always double check anyway. Just Google the card's tdp.
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a c 110 ) Power supply
June 10, 2012 5:14:12 PM

A good 430W would be the Corsair CX430V2.
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a b ) Power supply
June 10, 2012 5:57:50 PM

blackhawk1928 said:
Remember, current is a lot harder to produce at higher voltages.

PSUs do not produce current, they convert power and 12V power is much cheaper (lower currents for a given power), easier (wider tolerances) and more efficient (proportionally lower I2R and diode losses) to provide than lower voltages so there is no reason for PSUs of any price or quality to inflate their ratings using lower voltage rails. Because of that, PSUs that have ridiculously high rating on 5V or 3.3V rails are quite uncommon.

blackhawk1928 said:
If you have a 1000watt psu but just ten amps on your 12V...it wont handle a damn thing.

If you compare a random sample of 200-300W PSU with a random sample of 1200-1800W PSUs, you will notice that the bigger PSUs only provide 100-150W more power on 3.3V+5V combined. Nearly all extra power is dedicated to 12V rail(s).

Sure, there are some oddball PSUs with anemic 12V rail(s) but for the most part, they are few and far between since low voltage rails are an expensive way to inflate ratings with something almost nobody needs anymore.
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June 10, 2012 6:05:19 PM

why make things so complicated.. i dont understand half of this anyway..
just tell me how much watt i need to buy according to what I gave above..
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a c 158 ) Power supply
June 10, 2012 6:17:27 PM

The Antec EA-380D is a good option for your PC. The Corsair CX430 is also another good option. Both of those options are based on a purchase in the US...budget and location affects recommendation. What is your budget? Where are you shopping?
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a b ) Power supply
June 11, 2012 12:55:21 AM

InvalidError said:
PSUs do not produce current, they convert power and 12V power is much cheaper (lower currents for a given power), easier (wider tolerances) and more efficient (proportionally lower I2R and diode losses) to provide than lower voltages so there is no reason for PSUs of any price or quality to inflate their ratings using lower voltage rails. Because of that, PSUs that have ridiculously high rating on 5V or 3.3V rails are quite uncommon.


If you compare a random sample of 200-300W PSU with a random sample of 1200-1800W PSUs, you will notice that the bigger PSUs only provide 100-150W more power on 3.3V+5V combined. Nearly all extra power is dedicated to 12V rail(s).

Sure, there are some oddball PSUs with anemic 12V rail(s) but for the most part, they are few and far between since low voltage rails are an expensive way to inflate ratings with something almost nobody needs anymore.


-Don't nit pick on my wording. I was trying to make it easier for the OP. Want to get technical? Lets have at it :) . The PSU will convert/rectify current to DC as soon as it gets it but will turn it into AC once again. It will then bump the frequency to really high levels for efficiency so you can use a tiny transformer to get back into DC. Otherwise PSU's would be the size of tanks...and probably weigh as much also. Efficiency rises with frequency in AC. Also I think you are very wrong in this statement, but I could also be wrong...just basing this from what I know.

Quote:

they convert power and 12V power is much cheaper (lower currents for a given power)


Semi-conductors are MUCH more expensive to make to operate at higher voltages, no?...not higher current. Voltage variety affects price a lot more than current variety in this specific case.
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a b ) Power supply
June 11, 2012 2:49:07 AM

blackhawk1928 said:
It will then bump the frequency to really high levels for efficiency so you can use a tiny transformer to get back into DC. Efficiency rises with frequency in AC.
Actually, pushing frequencies higher make it increasingly difficult to achieve high efficiency due to skin effect in conductors, parasitic inductance, transient losses when diodes and switching elements (MOSFET, IGBT, bipolar) switch on/off, increased gate/base drive power for switching elements and synchronous rectifier output MOSFETs, higher Foucault (eddy) current losses in the magnetic core and filter chokes, etc.

For highest efficiency, you want to use the lowest frequency that makes it possible to fit the required components in the available budget, space and weight limits.

2555523,17,339378 said:
Semi-conductors are MUCH more expensive to make to operate at higher voltages, no?
[/quote]
said:

Under 50V, voltage has almost no effect on most discrete semiconductors' manufacturing costs and if you look at bulk pricing, many devices across the 4-50V range are priced within pennies from each other in reels of 2500+.

If you do the same exercise comparing 5A (useless for PC PSU output rails) with 50A devices (more in-line with what would be used for PSU outputs) on the other hand, the difference jumps from pennies to nickels and dimes.

In low-voltage applications, current drives costs up much faster than voltage does.
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June 11, 2012 4:41:45 AM

ok forget it you can't answer a simple ******* question...
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a b ) Power supply
June 11, 2012 5:51:06 AM

I answered you about 10 posts ago. 400 to 500 watts.
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June 11, 2012 6:20:08 AM

It's about power consumption, and, as pointed out in the Toms build article, your system just doesn't require a whole lot
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a c 110 ) Power supply
June 11, 2012 6:23:39 AM

Pokeliz said:
ok forget it you can't answer a simple ******* question...

Or maybe you can't read :whistle: 
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Best solution

a b ) Power supply
June 11, 2012 6:37:36 AM

Pokeliz said:
ok forget it you can't answer a simple ******* question...


You received two replies...after that you proceeded with another question which was then once again...answered by another post. Do you want another opinion? I think a 450-500watt PSU should be fine. Just do not cheap out. Do you have lots of fans/HDD's/extra cards or addons?

I think this corsair is fine. I do not know about the quality of the CX Series in general, but I've used one and it works great.
http://www.corsair.com/us/power-supply-units/cx-series-...

If somebody knows of any reliability issues or concerns, please say so. I know that the AX, TX, and HX are some of the best on the market though...just expensive however.
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June 11, 2012 9:44:05 AM

blackhawk1928 said:
You received two replies...after that you proceeded with another question which was then once again...answered by another post. Do you want another opinion? I think a 450-500watt PSU should be fine. Just do not cheap out. Do you have lots of fans/HDD's/extra cards or addons?

I think this corsair is fine. I do not know about the quality of the CX Series in general, but I've used one and it works great.
http://www.corsair.com/us/power-supply-units/cx-series-...

If somebody knows of any reliability issues or concerns, please say so. I know that the AX, TX, and HX are some of the best on the market though...just expensive however.


Thank you ! it is 500W and kida cheap so i thick i'll buy something like that..
and I was little mad (not because i cant read) because i don't know in a bit with all that volts and DC's and stuff so it doesn't mean anything to me..
So I've got the answer i needed, really thank you all..!

and I really don't have lots of fans' HDD and stuff.. (:
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June 11, 2012 9:44:14 AM

Best answer selected by Pokeliz.
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!