The rules of electricity and physics still apply. If you're pulling a set amount from the wall, once it goes through the power supply and is converted to DC, there's going to be some losses and wastage. It can only be in one direction - down!

 

If you can draw 200W from the wall but have 300W being drawn from the power supply, then you have a Nobel Prize in your future. Or a separate power cable to your power supply.

 

Adding up the specs isn't a bad idea - I did that with the TDP on my CPU and GPU and discovered that they didn't exceed 200W.

 

Cheers!

 

Luke

Never said the laws of physics didn't apply and I didn't say that you would have more wattage drawn from the pwo3er supply than from the wall.

 

However, I did say that ac and dc are two different critters and they are. I also said that the best method of figuring out what size PSU is needed is to take a look at the specs for everything in the system and add up the wattage requirements.

 

As just a small illustration of things, I have a 35 amp, 12VDC, power supply for radio equipment. I regularly draw a good 30 amps out of it measured inline at the output of the power supply... it's running on a 120VDC circuit protected by a 15 amp circuit breaker. Of course, plugging those values into a wattage calculation means I am barely drawing 3 amps out of the wall to drive my 12VDC power supply at 30 amps (360 watts).

 

 

 

As just a small illustration of things, I have a 35 amp, 12VDC, power supply for radio equipment. I regularly draw a good 30 amps out of it measured inline at the output of the power supply... it's running on a 120VDC circuit protected by a 15 amp circuit breaker. Of course, plugging those values into a wattage calculation means I am barely drawing 3 amps out of the wall to drive my 12VDC power supply at 30 amps (360 watts).

 

I think we're in agreement - the only caveat I would have is that one should look at the CPU+GPU TDP rather than the rated specs. GPU manufacturers radically overstate their PSU requirements because there are a ton of crappy power supplies out there.

 

Cheers!

 

Luke

Luke, I agree. There are a lot of crappy PSUs on the market. However, I like taking equipment manufacturers at their word mostly. There have been times I felt I 'knew better' and found out I didn't... Now, I tend to go a bit the other way and 'over engineer' things.

In my radio example, I installed the same model radio in my vehicle. The manufacturer suggested a minimum of 10 gauge wire for supplying power... turns out the manufacturer was right! I tried smaller wire, 14 gauge, and had terrible operation... increasing the size of the supply wire, and reducing resistance, cleared everything up.