Sign in with
Sign up | Sign in
Your question

Is my PSU enough

Last response: in Components
July 31, 2010 7:12:40 AM

HI all i am currently running a C2D e7400 4 gb ddr2 800 mhz ram and a sapphire 4670 1 gb edition and a 320 gb WD HDD my PSU is 400W and it gives 12 amps on the 12 v rail is it enough any help wold be highly appreciated

More about : psu

a b ) Power supply
July 31, 2010 8:58:34 AM

Your PSU gives very low output and 12A on 12V is certainly not enough for your rig.. Get a better PSU...
a c 139 ) Power supply
July 31, 2010 1:27:04 PM

Is there more than one 12v rail? Can you tell us the make and model of the PSU?
400w and only 12amps of +12v isn't something we expect to see.

Usually a 400W PSU is more than enough for the hardware you list.
Related resources
a c 139 ) Power supply
July 31, 2010 1:35:12 PM

I did find a 300W PSU with just 15amps of +12v. It also have a -5v rail that points to an old school PSU.
Check the data label on your PSU and see if you have a -5v rail as well.

August 1, 2010 6:04:30 PM

12A on the 12V rail is really low. How old is it? I just replaced a really bad power supply and it had 22A on the 12V rail.

I'd suggest using a PSU calculator to get a rough estimate of how much power you are using. Here are two:

Generally, you want your power supply to deliver more than your required wattage to account for PSU inefficiencies. Some technical help sites and forums suggest up to 50%, though it's up to you how much of a safety blanket you want .
a c 139 ) Power supply
August 1, 2010 6:20:10 PM

sf_torquatus said:
Generally, you want your power supply to deliver a lot more than your required wattage to account for PSU inefficiencies. Newegg suggests a PSU that delivers twice what you need. It's up to you to follow that advice or not.
Does NewEgg actually say that? Double what you actually need?

August 1, 2010 6:47:48 PM

I thought they did, but I went back and checked and couldn't find it. I've been searching so many web sites in the last week, especially about PSUs, appeared on one of them. Though, when I did another internet search I found this thread:

It seems as though you like the 70-85% full-load/30-50% idle figures. I guess it all comes down to preference and balancing the "Having too much power and being super safe" ideals with "Choosing a model closer to your own power draw to be more efficient".

All I can go on now is my own experience. That experience says I bought a replacement PSU too close to the estimated power demands and it doesn't work. Personally though, I think the OP would be fine with a 400W-500W supply since doubling it and going for 700-800W seems a little overkill.

I'll edit the original post to fix the citation error :) 
a c 139 ) Power supply
August 1, 2010 7:28:35 PM

The quality of the PSU is every bit (and maybe more important) than the quantity of power it's rated to provide.
We like to see PSU's torture tested to 100% of its rated capacity by the better review sites like JonnyGuru, HardOCP, HardwareSecrets and a few others. If you get a top rated PSU from one of those sites it's less of an issue if someone looks to be nearing 80% capacity.

Since the OP's system is going to pull less than 200watts DC, maybe 260watts AC if his PSU is 70% efficient a good 400W PSU is certainly generous. Of course we're guessing since we don't know what that 12amp +12v PSU is. Personally, I'm thinking it might be some type of dual +12 PSU.