Questions about power use

[purple]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

I want to build a very low power PC to act as my file and print server
for a home network. Sadly, I don't really understand "power" and was
hoping to get some advice.

I've been told that some devices use power/electricity even when you
are not using them. Specifically devices that have a "black box" which
plugs into the wall and a tiny DC connector. I assume the black box is
a transformer/power converter (AC to DC) and that this uses energy
even when the machine it supplies isn't on.

With this in mind, I've been wondering whether a PC power supply
similarly uses energy even when there is not much load. For instance,
say you get a 350Watt power supply and have an old Duron700 with a CD
drive and 1 hard drive… Is this system wasting power even though it
doesn't need 350W? I understand that having an undersized power supply
causes problems but does having an oversized power supply waste
energy?


Im going to try a VIA M1000 EPIA motherboard for my server. The Morex
cases for this board include a 60W powersupply but they only have room
for one harddrive and I need room for 2. My next case choice is an
Antec Minuet but its power supply is 220W…

Going from 60W to 220W is a big jump and I am assuming that my little
system will not need so much power. I just want to know that using a
larger power supply wont negate my intentions for the lower power CPU.

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Purple wrote:

> I want to build a very low power PC to act as my file and print server
> for a home network. Sadly, I don't really understand "power" and was
> hoping to get some advice.
>
> I've been told that some devices use power/electricity even when you
> are not using them. Specifically devices that have a "black box" which
> plugs into the wall and a tiny DC connector. I assume the black box is
> a transformer/power converter (AC to DC) and that this uses energy
> even when the machine it supplies isn't on.

Yes, it's a little transformer/power converter and while 'technically' it
uses some power when the connected device is off it's insignificant.


> With this in mind, I've been wondering whether a PC power supply
> similarly uses energy even when there is not much load.

An ATX power supply ALWAYS has the standby voltages on. 'Off' simply turns
off the heavy power ones.

> For instance,
> say you get a 350Watt power supply and have an old Duron700 with a CD
> drive and 1 hard drive… Is this system wasting power even though it
> doesn't need 350W?

Well, possibly, but that's a matter of where the power supply's maximum
efficiency point is and not all that easy to find out. It's not large,
compared to the PSU rating, but it's probably more than what the wall unit
would 'waste'.


> I understand that having an undersized power supply
> causes problems but does having an oversized power supply waste
> energy?



> Im going to try a VIA M1000 EPIA motherboard for my server. The Morex
> cases for this board include a 60W powersupply but they only have room
> for one harddrive and I need room for 2. My next case choice is an
> Antec Minuet but its power supply is 220W…

You can get lower power units than that, you know.

>
> Going from 60W to 220W is a big jump and I am assuming that my little
> system will not need so much power. I just want to know that using a
> larger power supply wont negate my intentions for the lower power CPU.

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Purple" <vaitkus@pacbell.net> wrote in message
news:d9a19377.0407011702.2bf68b24@posting.google.com...
> I want to build a very low power PC to act as my file and print server
> for a home network. Sadly, I don't really understand "power" and was
> hoping to get some advice.
>
> I've been told that some devices use power/electricity even when you
> are not using them. Specifically devices that have a "black box" which
> plugs into the wall and a tiny DC connector. I assume the black box is
> a transformer/power converter (AC to DC) and that this uses energy
> even when the machine it supplies isn't on.
>
> With this in mind, I've been wondering whether a PC power supply
> similarly uses energy even when there is not much load. For instance,
> say you get a 350Watt power supply and have an old Duron700 with a CD
> drive and 1 hard drive. Is this system wasting power even though it
> doesn't need 350W? I understand that having an undersized power supply
> causes problems but does having an oversized power supply waste
> energy?
>
>

Power ratings are maximums. If your PC uses 100W continuous, that is what
it will use. It can use UP TO 350 watts for short periods of time without
over-stressing your power supply, but if it only needs 100W, that's what it
will use. -Dave

 

[user]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

Purple wrote:

> I want to build a very low power PC to act as my file and print server
> for a home network. Sadly, I don't really understand "power" and was
> hoping to get some advice.
>
> I've been told that some devices use power/electricity even when you
> are not using them. Specifically devices that have a "black box" which
> plugs into the wall and a tiny DC connector. I assume the black box is
> a transformer/power converter (AC to DC) and that this uses energy
> even when the machine it supplies isn't on.
>
> With this in mind, I've been wondering whether a PC power supply
> similarly uses energy even when there is not much load. For instance,
> say you get a 350Watt power supply and have an old Duron700 with a CD
> drive and 1 hard drive… Is this system wasting power even though it
> doesn't need 350W? I understand that having an undersized power supply
> causes problems but does having an oversized power supply waste
> energy?
>
> Im going to try a VIA M1000 EPIA motherboard for my server. The Morex
> cases for this board include a 60W powersupply but they only have room
> for one harddrive and I need room for 2. My next case choice is an
> Antec Minuet but its power supply is 220W…
>
> Going from 60W to 220W is a big jump and I am assuming that my little
> system will not need so much power. I just want to know that using a
> larger power supply wont negate my intentions for the lower power CPU.

Buy a Power Supply with 'Power Factor Correction' if you're concerned
about your electrical bill.

Interesting article:

http://www.silentpcreview.com/article79-page2.html

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

> I've been told that some devices use power/electricity even when you
> are not using them. Specifically devices that have a "black box" which
> plugs into the wall and a tiny DC connector. I assume the black box is
> a transformer/power converter (AC to DC) and that this uses energy
> even when the machine it supplies isn't on.
>
> With this in mind, I've been wondering whether a PC power supply
> similarly uses energy even when there is not much load. For instance,
> say you get a 350Watt power supply and have an old Duron700 with a CD
> drive and 1 hard drive. Is this system wasting power even though it
> doesn't need 350W? I understand that having an undersized power supply
> causes problems but does having an oversized power supply waste
> energy?

A supply that is much larger than needed may use slightly more power than
one that is just able to supply the correct ammount of power. It will not
really be noticed in the power bill in a years time. Sort of like a brick
being added to a truck. It is there but small enough it is not noticed.
It only uses the ammount of power the computer boards and hard drives need.
A 200 watt supply and a 400 watt supply will draw almost the same ammount of
power from the AC plug if they are powering the same computer boards,
processor and drives.

Use the larger supply and if you later need to add another hard drive it
will be there.
It will not watse any more noticable energy.

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Purple" <vaitkus@pacbell.net> wrote...
> I want to build a very low power PC to act as my file and print server
> for a home network.

Use a notebook if power is the primary concern, and you aren't worried about
performance.


> With this in mind, I've been wondering whether a PC power supply
> similarly uses energy even when there is not much load. For instance,
> say you get a 350Watt power supply and have an old Duron700 with a CD
> drive and 1 hard drive. Is this system wasting power even though it
> doesn't need 350W? I understand that having an undersized power supply
> causes problems but does having an oversized power supply waste
> energy?

A conventional ATX or EPS power supply will draw idle power even when the
computer is in sleep mode. Some is for fans, some is because the
motherboard draws some power in sleep mode. A newer MoBo with ACPI will
draw less than 5 watts in sleep mode, and something over 30 watts (depending
on processor and RAM) when operating, not including peripherals. The Intel
D915G MoBo, for example, supports a max of 300 watts of DC power draw via
the MoBo for all its cards and
peripherals(ftp://download.intel.com/design/motherbd/av/C6860001.pdf).


> Im going to try a VIA M1000 EPIA motherboard for my server. The Morex
> cases for this board include a 60W powersupply but they only have room
> for one harddrive and I need room for 2. My next case choice is an
> Antec Minuet but its power supply is 220W.
>
> Going from 60W to 220W is a big jump and I am assuming that my little
> system will not need so much power. I just want to know that using a
> larger power supply wont negate my intentions for the lower power CPU.

Check out the MoBo technical specs for actual power draw. Do the same for
all add-in cards and peripherals. Figure out what the typical and max power
draw will be.

A modern power supply is most efficient when working at a "typical" load of
approx 20-50% of its max rated load; the efficiency will be somewhat less at
high and low power draws. Find a power supply with the highest efficiency
rating you can, and sized accordingly.

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

"Dave C." <mdupre@sff.net> wrote...
>
> Power ratings are maximums. If your PC uses 100W continuous, that is what
> it will use. It can use UP TO 350 watts for short periods of time without
> over-stressing your power supply, but if it only needs 100W, that's what
it
> will use. -Dave

Not quite...

Maximum efficiency ratings are quoted for "typical" loads, approximately
20-50% of max rated load; efficiency drops off for lower and higher loads.
So, if the expected normal draw for a system is 100W, and all power supplies
have the same rated efficiency, choose a power supply between 200 and 500
watts for best efficiency.

Granted, that's a wide range, but other considerations (e.g., $$ and
projected max load) will help you decide which to buy.

 

[Guest]

Archived from groups: alt.comp.hardware.pc-homebuilt (More info?)

On Thu, 01 Jul 2004 22:06:43 -0600, )-()-( wrote:

> Purple wrote:
>
[snip?

>> Going from 60W to 220W is a big jump and I am assuming that my
little
>> system will not need so much power. I just want to know that using a
>> larger power supply wont negate my intentions for the lower power CPU.
>
> Buy a Power Supply with 'Power Factor Correction' if you're concerned
> about your electrical bill.
>
> Interesting article:
>
> http://www.silentpcreview.com/article79-page2.html

Yes, very interesting indeed. Especially the (completely most stupidously
one that I ever saw in an electrical power test report) statement which
tries to lure you into believing that:
"A PF of 0.5 means that to deliver 100W in AC to a PSU, your electric
company actually uses 200W and this is most definitely shown in your
electric bill.. 100W is lost or wasted."

This is complete rubbish.

This tester even hasn't a clue about the difference between reactive
power (which does definitely NOT -- shouting intended -- appear on any
small consumer's electricity bill) and active power (wich DOES appear on
the bill).
If the power consumed by the computer is for instance 100 Watts (yes:
'Watt', not Volt-Ampere) with a PF of 0.5, then the so called 'apparent
power' is 200 VA (expressed in Volt-Ampere), but the so called 'real' or
'active' power is still 100 W. And this real, or active power is the only
one appearin on the electricity bill of a simple consumer.
Big companies are billed for the reactive power they consume, as this one
increases the cable size needed to deliver the real power.

And there are more lies published on this page:
"PF is not ... , but it is very relevant to real electricity consumption
and energy conservation."

The same lie repeated.

Me assumes this 'test lab' is the companies own marketing department.

Flip

 

[cueballgeek]

Check out some of the articles floating around about Google and their power supplies for the servers in their datacenters. They went with lowest practical wattages to help minimize energy wasted as heat, which will also help save on cooling costs. I have an AMD64X2 4800 system with add-on video, dual DVD, dual HD's, case lighting...According to my UPS software monitor, the high-water mark for wattage use is only 235W. Do I need a 500W PSU? Probably not.