PSU Amps Question

[Kornowski]

I was wondering how to work out the total Amps a PSU has on both rails, I remember I worked out mine had 27A all together on both 12v rails, 17A on each. I have an Antec 380watt Earth Watts

I've seen 500watt PSU's that have the same Amps on the 12v rails and some with less, by brands like OCZ...

Well, The main question is, why are these lower than my 380watt PSU...

I'm considering an 8800 and they say you need 26A on the 12v rails, I'm 1 Amp over, don't the companies stick the requirments up so people are Ok...

What do you think?


Like this, I know it's a value PSU, but 52 good reviews and it has a higher Ampage than my current Antec...
http://www.ebuyer.com/UK/product/102994


I found this, people saying they have an 8800 on a 350watt PSU:
http://forum.ncix.com/forums/index....m=214&threadid=1218226&pagenumber=9&subpage=3

 

[Kornowski]

Anybody?

 

[Geoff]

I wouldnt go with the bare minimum when it comes to power requirements, especially if you plan to overclock. Personally I wouldnt get anything lower then a 500W for a single 8800GTS, and I would get at least 30A on the +12V rail(s).

As for figuring them out, I think it varies depending on the company and quality. Because i've seen some dual rails at 20A each that only put out a bit above 30A combined.

 

[Kornowski]

Ok, Thanks, I know, I'm a pain in the ass, it was just bugging me, It's strange how something can be called 500watt and be something more like a 300 watt, thanks for the help anyway

 

[Geoff]

Ok, Thanks, I know, I'm a pain in the ass, it was just bugging me, It's strange how something can be called 500watt and be something more like a 300 watt, thanks for the help anyway

The amps dont mean a 500W is more like a 300W, it simply means it has more amperage. For instance, you can buy a cheap 600W power supply with maybe 20-30A, but get a 450W power supply with 40-50A.

 

[StrangleHold]

I was wondering how to work out the total Amps a PSU has on both rails, I remember I worked out mine had 27A all together on both 12v rails, 17A on each. I have an Antec 380watt Earth Watts

I've seen 500watt PSU's that have the same Amps on the 12v rails and some with less, by brands like OCZ...

Well, The main question is, why are these lower than my 380watt PSU...

I'm considering an 8800 and they say you need 26A on the 12v rails, I'm 1 Amp over, don't the companies stick the requirments up so people are Ok...

What do you think?


Like this, I know it's a value PSU, but 52 good reviews and it has a higher Ampage than my current Antec...
http://www.ebuyer.com/UK/product/102994


I found this, people saying they have an 8800 on a 350watt PSU:
http://forum.ncix.com/forums/index....m=214&threadid=1218226&pagenumber=9&subpage=3

Sometimes on there sites like OCZ, Antec, Thermaltake, ePower will have how much the total Amps on the 12V rails have if not sometimes reviews will have it.

 

[ceewi1]

I was wondering how to work out the total Amps a PSU has on both rails, I remember I worked out mine had 27A all together on both 12v rails, 17A on each. I have an Antec 380watt Earth Watts

I've seen 500watt PSU's that have the same Amps on the 12v rails and some with less, by brands like OCZ...

Well, The main question is, why are these lower than my 380watt PSU...

This can be for a number of reasons. Older PSUs generally have lower amperages on the +12V rails, and many cheaper units will use a high wattage rating to try to lure in unwary customers. Sometimes it's just done to meet a pricepoint. There's also nothing wrong with PSUs with more power on the +5V rail, in applications where the 5V rail will be loaded heavily. It just means that the PSU can (or should be able to) put out a total of X Watts of power, with a certain amount of it on the +12V rails. In many (read most) cases, the amperage available on the +12V rails will be the limiting factor when assessing a PSU - modern PCs can draw ~90% of their power from the +12V rail(s). In that respect, a 380W PSU with +12V@27A may be able to power a system that a 500W PSU with +12V@22A can't.

I'm considering an 8800 and they say you need 26A on the 12v rails, I'm 1 Amp over, don't the companies stick the requirments up so people are Ok...

What do you think?

It's pushing the supply quite a bit, but should work.

Like this, I know it's a value PSU, but 52 good reviews and it has a higher Ampage than my current Antec...
http://www.ebuyer.com/UK/product/102994

I've got a really cheap 550W unit, rated for +12V@39A here, which I use for testing older PCs. Just for kicks, I tried putting it in a system including an A64 and PCI-E 6600. It wouldn't even POST. I've pushed similar units outisde ATX specs by running Prime95 on systems with integrated graphics. What you have to realize is that just because 30 or 39A is written on the label isn't necessarily a good indication of how much power the unit can actually put out.

A lot of times these reviews are either written by people with systems with really low power requirements, which can't even push these power supplies, or by people who couldn't tell a PSU from a brick. They're also usually written soon after purchase with no indication of long term reliability.

I can (but don't have time to right now) provide links to a number of PSUs which receive great user reviews, but are objectively proven to blow (sometimes dangerously) at around half their rated output when tested properly.

 

[Kornowski]

Wow! Thanks for the reply Ceewi1!

So, I guess it means the PSU I have is a good quality one, I'm glad you helped me make the right decision when buying it

Yeah, I guess the reviews don't really tell you much, or give you an indication if the product is any good.

As far as the 8800 goes, it was a lot of money and I don't plan on getting Vista, so I wouldn't of been able to use DX10, so I went ahead and bought a 7950GT, it should be Ok with the DX9 games! and some future ones...

Thanks again