Q: Power supply watts

[Canon]

Hi, I have a question on power supplies. Does the amount of watts they provide, matter? I mean is there a difference between a 250 watts supply to a 400 watts supply, to an average user?
And what does the watts measurement do? Does it specify how much components are allowed to be hooked up into the computer,(as it it can only have a certain number of hd's and fans)?

[Steve R Jones]

There is no day to day difference if you have enough wattage. If you only have 250 but have enough hardware to require 300 or more you'll have troubles. Your pc will lockup, shutdown etc.....

[Psycho Logical]

For some background, see: The Power Supply (http://www.pcguide.com/ref/power/sup/index.htm) section in The PC Guide (http://www.pcguide.com/index.htm)

[Canon]

I've read that site you suggested, but how do I know if I've hit my limit of adding stuff into my comp?
I have a PCI to IDE card that allows me to place in 4 more drives . . . I'm worried that the power supply won't be able to handle that, along with the multidudes of fans I have in there already

[Steve R Jones]

You'll know when you run out http://www.sysopt.com/forum/smile.gif What size do you have now?

[Vagabond]

all of your hardware specs should containg their wattage usage. Add them up.. and there ya go..

[Bsdboy]

Here (http://www.pcworld.com/howto/article/0,aid,52328,pg,3,00.asp) is a chart to help you figure out your power needs.

Bsdboy

[justy]

Quick shatter to some myths!

Amount of watts, does not always mean P.C. is getting all it wants. If You have a 30amp 12volt rail ( 360watt ), and a 18 amp 5 volt rail, it doesn't mean your trucking.
All that, that means is you have a nice 450watt PSU that wont run your P.C.

Buy a PSU, based on what your consumption is. i.e. I'm posting this on a dual celeron BP6 with a video capture card, a matrox video card, a sound blaster live, 3 hard drives, a dvd drive, a cd rw, and 5 fans.
The PSU is rated at 230 watts!

I reckon, I could get another 7 fans, and 4 drives, if I could find somewhere to fit them!

What I am saying is, Current at the different voltages is important. There is no use buying a high wattage PSU, that has its resources stacked towards a supply that you are not using.

Arguments?

All the best, Justy.




[This message has been edited by justy (edited 07-12-2001).]

[Graham]

Justy,
None.

G

[Psycho Logical]

These are not the only considerations.

Disregarding the whole rails thing for a moment, power supplies in general are only
65-80% efficient. A PS marketed as 300-watt actually only delivers 195 to 240 watts total.

The peak demand may far exceed the 'steady state' demand.
HD's require far more current to start up than they do to read, write, or idle.
CD-RW's need much more to actually burn than they do to read.

Also, a PS will run cooler/last longer if the average load is around 75%.

Using average values from above on a 300-watt PS:

300 watts (nameplate) x 72.5% efficiency x 75% load = ~ 163 watts.


[This message has been edited by Psycho Logical (edited 07-13-2001).]

[justy]

Well done! ( not meant in a bad way )!

You only add to what has been said.

More time spent on what we need, less on sales talk.

All the best, Justy.