What uses power?

Hi all.
What makes the need for a 550W psu over a 350 W psu, even if they are the same make.

I need a PSU for
A64 3400+ @ 2.4GHz
128 FX5500 Graphics
2 Optical drives

What power is suitable?

(PS - i am using a £27 550W psu for my current system and it is not having stability issues - is 550W too much for my current system??)

No such thing as too much power. The nice thing about power supplies is that you can continue to use them until they don’t work any more. Four screws and unhook some plugs and off to a new case. You may need an adapter or two but other than that they are completely portable. And to answer your question, if it isn’t broke, don’t fix it.

i am making a new system (for which i will use my old PSU, and I’ll buy a new PSU for my old system), and so nothing is broke. by “too much” i meant “more than necessay” because high power psus of the same make cost more.

you can check your power consumption here if you want to give you a rough idea of the power supply you need


i go by the rule of you can never have too much power, however make sure you don’t buy cheap power supplies. 550W for £27 sounds too good to be true, its probably not a true 550W. I’ve bought a couple of cheap PSU’s in the past and they always bugger up really fast.

I used cheap PSU’s for years, until I got into overclocking. I wore out three PSU’s in just one night!

But okay… you have a 550W, that is nice. Question is: how much power can be delivered per rail? Especialy the +5V and the +12V rails matter quite a lot (A64 really needs more than 15A on the 12V rail)? As long as your system is running fine I wouldn’t worry, but it’s most certainly something to keep an eye on when buying a new system.

I wouldn’t go with cheap PSUs btw (for various reasons).

i am willing to risk a high power rated cheap psu on price grounds. I don;t overclock btw.

My system is 311W.

but if i am going to go for a cheap psu, shouldn’t i just go for a 350W rated one, or am i better off going for a higher rating.

If you want a cheap PSU, you should really consider 400W or more for a 311W consuming system (how did you calculate that btw)! I’d even advice to go for a 500W or higher rated PSU.

Considering the price of the cheap 500W PSU, you also might consider a good 350W PSU. Chances are big that the 350W (from a brand like Zalman for example) does better than a cheap 500W one. Also, stability will be better, noise- and heatproduction will be lower.

i might do that.

(btw i calcualted the rating after thinking more carefully about whihc components will be in my new and old systems lol)

My advice is to stay on the safe side and make sure there’s some room left. That will allow you to do upgrades and give you some space right now… it’s not good to push your PSU to it’s limits all the time (generates more heat, shortens the life of your PSU and possible destabalizes the delivered power).

Would you build a Ferrari and then put in a VW motor?

Listen to what Dee-ehn said a few posts back. The rated output is not the whole story. If it can only deliver 200W on the 12v rail, it’s not going to cut it. Most better PSU carry ratings for each rail. Most of what you are putting in there will be on the 12v rail. I had a Antek 550 blow up (literally) on this power hog, but a Thermaltake 480 is doing just fine.

If you want to check out the system and PSU, just use a good voltage monitor to watch the values on each rail, if they vary by more than 5% you may have a problem.

A modern PC will pull quite a bit of current from the +12V DC rail. The loads on the +3.3 and +5V rails are usually much lower. This is good, because the reserve power can be redirected to the +12 V rail. People don’t burn at 16X and play 3D games at the same time. The maximum load on the PS usually occur with 3D games with sound card, optical drive, hard drive, and video card active.

If the +12V DC rail is rated at 20A or better, then PS should be able to deliver sufficient juice to run the system.

What brand is that 550W psu?

‘golden power with a 12cm fan’ . how do i check the current ratings for my psu? i think it came with no stickers (ill check next time i open my pc)

This is good because i do play games, but with no sound card or optical drive and only 1 HDD

You’ll never know. Google might turn up your data, but with class of products you won’t know if the real performance does get close to it… (most likely it won’t).

Don’t take it that literal. Modern CPU’s can use up to 90 watts (AMD) or 130 watts (Intel), modern videocards do about 80 watts. The powerconsumption of the other components are relatively small.

20A on the 12V is really needed for modern systems. The A64 alone requires a minimum of 12A on the 12V line! Depending on your video card and the other components, you might need another 10A or so.

To juice my system I have a Levicom (German brand, not known but a well performer) PSU with a rated capacity of 550W. It does 35A on the 12V line… I had stability issues with a 12A model. My system? Athlon 64 3200 @ 3500, Radeon 9700 @ pro, 4hdds, 4odds and some fans + lights. Not THAT much eh?

i had a similar experience when i overclocked, for ages my PSU kept making stupid sounds, so i just kept bashing it till one day it just gave up on me. And then it happened again, and again…

Great link. :bow: Thanks for pointing it out.

Whenever your PSU starts to make strange noises (high tones), better get rid off it because it will fail quite soon :slight_smile: