Is this PSU enough for me?

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sttiger

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Feb 21, 2014
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hi every one i had the following system:
intel g620
HDD 1TB WD green
mainboard Asus p8h61/usb3
Vga: GT240 2G ddr2
optical drive: pioneer DVD RW
PSU: Memonex silentex 370W
I upgraded the VGA to sapphire radeon 7750 1G and i want to know is my PSU enogh or not?
and there is a table on the PSU that says it has 28amps on combined +12v rails
Thank you
 
Solution
bicycle_repair_man
Well, Sapphire recommend a 400W minimum PSU for that card. Granted, that's to cover a wide range, including the cheap knock-offs.

http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=1454&lid=1#

Just by looking at your spec, I'd say that you're cutting it very fine at 370W with dual +12V rails and 28A. That 370W figure will be comprised of +12V, -12V, +3.3V, etc but most of your components will use +12V. If you do the calculation ampere (28) x volts (12) = wattage (336) you get an idea of how much wattage you REALLY have. I don't think that 336W will be enough.

You also need to consider the fact that your PSU has dual +12V rails, so the power is being split two ways. In theory, the PSU should be smart enough to...
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ServiceDroid_R

ServiceDroid_R

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Feb 19, 2014
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4,520
Try this site:
http://support.asus.com/powersupply.aspx

I filled it in with your details (although I might not have been 100% accurate) and it recommends a psu with 350 watts, your psu has 370watts. That might be a bit too close for comfort, probably be a good idea to upgrade the psu as well.

Although, it'd probably be a good idea to look at the website and do your own calculations as well.
 
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sttiger

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Feb 21, 2014
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are you sure about that? im new to computer and i dont know alot but i found this wbsite http://www.hwcompare.com/12982/geforce-gt-240-gddr5-1gb-vs-radeon-hd-7750/
that says gt240 max TDP is 70W and 7750 max TDP is 55W
What is TDP? is it the power that vga needs?
 
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bicycle_repair_man

bicycle_repair_man

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Jan 10, 2014
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Well, Sapphire recommend a 400W minimum PSU for that card. Granted, that's to cover a wide range, including the cheap knock-offs.

http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=1454&lid=1#

Just by looking at your spec, I'd say that you're cutting it very fine at 370W with dual +12V rails and 28A. That 370W figure will be comprised of +12V, -12V, +3.3V, etc but most of your components will use +12V. If you do the calculation ampere (28) x volts (12) = wattage (336) you get an idea of how much wattage you REALLY have. I don't think that 336W will be enough.

You also need to consider the fact that your PSU has dual +12V rails, so the power is being split two ways. In theory, the PSU should be smart enough to distribute power as it's needed, but I wouldn't trust your one to do that.

Get yourself a good 450W or 500W PSU from the likes of Corsair or Cooler Master, preferably one with a 80+ Bronze rating. Look for a single +12V rail with around 35A-40A.
 
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Solution
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sttiger

Reputable
Feb 21, 2014
11
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4,510
oh i forgot to say that the 7750 is on my system now and system is working and even i played with it and i didnt see any problems. do you think if the power wasnt enough system should worked fine? or maybe it would stop after a while? And plz sorry for my bad english!
 
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bicycle_repair_man

bicycle_repair_man

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Jan 10, 2014
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If the PSU wasn't up to scratch, the PC wouldn't boot. I'd run your new spec through the PSU calculator again and see what figure you come back with. A typical PSU works most efficiently at around 60% load, but go for 85% or 90% so you can be confident that everything will be stable when your PC ramps up.

A higher wattage PSU gives you more scope for upgradability. As the OP has already upgraded the GPU, other components could be on the cards. You also don't want to run the PSU at 80% load when the PC is idle, give it room to breathe.
 
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