Are the other specs on a power supply important?

[Bidybag]

I never really understand all the specs on a power supply. I just look at watts. Are the other specs important? Does it actually make a difference if you had a cheap 700 watt and an expensive 700 watt, what would change?

 

[tkgclimb]

Yes the other specs are important, probably the most important is the watts on the 12v rail or rails because that will decide what Kind of video card you will be able to use.
And also there is a difference between cheap and expensive (name brand) power supplies Not only the amps on the 12v rail but also just the lasting quality. A CHEAP one may damage your system or die off quickly, and expensive ones are usually more efficient meaning they generate less heat, last longer, and use less energy, meaning you can get a lower wattage one.

FOr expample You would be better of to run a nice 380 watt PS of an system that draws 300 watts then a crappy 450

 

[jsc]

Specifications:

First: voltage - voltage tolerance is supposed to be +/- 5%.

Second: current. The 12 volt rating is critical. You want a high current rating. A 550 watt PSU should have at least a 40 amp rating at 12 volts. 650 watt - 50 amps; 750 watts - 60 amps. The 12 volt outputs feed the CPU and video cards. An overclocked Q6600 and a GTX260 pull about 20 amps by themselves.

On the other hand, 5 volt and 3.3 volt outputs higher than 10 amps each is wasted capacity. For example, the 3.3 volt output powers the memory. 2 GB of RAM needs about 3 amps at 3.3 volts.

Temperature rating: This is the temperature that the PSU is rated for full power. This is frequently overlooked. Most bottom end PSU 's are rated at 25 C. (room temperature) or they do not say - which means 25 C. The good PSU's are rated full power at 50 C. This is difficult enough to do that anyone who can will tell you about it. This is important because as a PSU heats up, it produces less power. I have seen derating (reduced output) curves indicating the loss of 1% - 2% per degree C. over the rating temperature. A PSU rated at 500 watts at 50 C. will produce 500 watts of power at 40 C. (104 F). A PSU rated at 25 C will produce 350 - 425 watts at 40 C. if you are lucky.

Build quality: Not part of ratings, but really important. Better PSU's use better components and heavier heatsinks. Compare two 500 watt PSU's. The heavier one will be the better one. Better PSU's are generally more quiet and efficient. The better PSU's are more conservatively rated. If most other PSU manufacturers made something like a 750 watt Corsair, they'd call it a 900 watt PSU.

 

[jpboyrox]

I have this power supply: http://www.misco.co.uk/applications/SearchTools/item-details.asp?EdpNo=331709&CatId=0

and a GeForce 9800GT is this reasonable or should I invest in a more expensive power supply?

 

[masterjaw]

I have this power supply: http://www.misco.co.uk/applications/SearchTools/item-details.asp?EdpNo=331709&CatId=0

and a GeForce 9800GT is this reasonable or should I invest in a more expensive power supply?

If you are planning to upgrade then do so. If not, then stick with it for a while.

 

[megamanx00]

Better PSUs last longer and are more stable. If you want some more info look into PSU tiers

http://www.eggxpert.com/forums/thread/323050.aspx

Basically the lowest you should go is a Tier 4. I say go for a tier 3 or better PSU. FSP, Antec, PC Power & Cooling, and Corsair are usually good bets ^_^.

 

[amnotanoobie]

Other cheap PSU's also sometimes rack up the 5V or 3.3V amperage just to increase the overall wattage.

 

[jsc]

Other cheap PSU's also sometimes rack up the 5V or 3.3V amperage just to increase the overall wattage.

That's not exactly what is going on. What is happening is that too many power supplies are based on old designs where the heavier 5 volt rails used to be important. Then they take the now obsolete designs and simply "modernize" them by adding the now required cables such as the PCI-e power and SATA cables.

 

[masterjaw]

Nice info there, jsc.