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From: smlunatick on 9 Feb 2010 10:00
On Feb 9, 11:46 am, JohnSmith1 <JohnSmi...(a)discussions.microsoft.com>
wrote:
> Hi,
>
> I would like to change my power supply but don't know what to get. Is there
> any software that will tell me about my current power supply and recommend a
> new one.
>
> thanks.

Sorry, but without a more detail question and with what you had
posted, this would lead people to believe that you might not have the
"know-how" to replace it yourself.

If you are not comfortable with "opening" your PC, bring it to a
repair centre.
From: Paul on 9 Feb 2010 11:44
JohnSmith1 wrote:
> Hi,
>
> I would like to change my power supply but don't know what to get. Is there
> any software that will tell me about my current power supply and recommend a
> new one.
>
> thanks.

To start with, not all supplies are of standard design. The vast majority
are, but there were some machines where the wiring harness is wired differently
than the standard. In some cases, the supply may even have an extra connector
on it, which you can't find on a store-bought supply. You can start by comparing
wire colors on your main harness, to the colors stated in the standard. That might
give you a hint your supply is not standard. Googling your computer name and
"replacement power supply" wouldn't hurt either. There may be hints there, as
to whether it is standard or non standard. For the mechanically smaller supplies, the
main problem with substitutions there, is the form factor - getting a
unit that fits, and the screws line up, the fan points the right way, and so on.
For full sized ATX supplies, that is less of an issue. (You can still have problems
with screw holes, but it is less likely to be a total flop.)

(Three generations of ATX standards...)

http://web.archive.org/web/20030424061333/http://www.formfactors.org/developer/specs/atx/ATX_ATX12V_PS_1_1.pdf

http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf

http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

*Every* rating on the supply label is important. There is a label printed
on the side of the supply, with the limitations of power in watts for the
total supply, current limitations for individual rails and so on. Buying
a supply with larger capacity would ensure those limits are met, and would
not require evaluating the hardware components inside.

It is possible to calculate (in a rough fashion), the needs of a particular
set of hardware. For example, if you were planning on adding a large video
card to the computer, it is possible the manufacturer of the computer
did not provide enough power, for any possible upgrade. In such a situation,
you take the hardware inventory (disks, optical drives, processor type,
all the jazz inside the box), and then do a calculation. (I've probably
done the calculation a hundred times in USENET posts, and it is relatively
easy to do.)

There are also a few web based calculators, but some of them end up
computing a power supply size which is double what is required. Which
is why I won't be posting any web URLs to such sites. (You could close your
eyes and just randomly point at the web page on Newegg with all the power supplies
listed, and get as accurate an answer.) The only web site that did a good job,
closed a number of years ago. Takaman used a spread sheet approach, so you can
see the numbers each item involved, and use your own technical judgment as to
whether they're accurate or not. The defunct web site page is archived, so you
can play with this tool, but since the web page is so old, I don't recommend it
for recent computers, as it is for a previous generation of hardware.

http://web.archive.org/web/20040411032947/http://www.takaman.jp/psu_calc.html?english

In terms of computer architecture, the power supply is not "plug and play". There is
*no* digital interface, between the power supply and the computer. The computer
software cannot "query" the power supply, and ask for details. All the computer
knows, is it is powered, but not how good, not how much margin or extra capacity
is available. Only a human can gauge what is going on, since the power supply
can be made cheaper by making it "dumb". It is possible in theory, to fully
instrument a power supply, to give all details. But then you'd have a whole wall
of dials and indicators on the side of your computer, and it would look like
you were flying the Space Shuttle. You can't make a power supply for $20,
if you put instruments or intelligence in it.

Paul
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