Re: [gentoo-user] Sizing up power supplies [was: switching adapter - power supply]

[Dale]

Alan Mackenzie wrote:
> Hello, Dale.
>
> Apologies to Thelma for hi-jacking the thread so early, but this point
> is too interesting just to pass over:
>
> On Mon, Mar 20, 2017 at 12:57:00 -0500, Dale wrote:
>
> [ .... ]
>
>> I might add, when I buy power supplies for my puter rigs, I try to buy
>> one that will only be loaded at around 40 to 50%.
> Do you mean 40 to 50% when the computer is going full blast (?like
> building libreoffice, or something like that).

I usually calculate for max power, yes.  After all, when running Gentoo
and compiling things like LOo, gcc and other large and lengthy packages,
there is a heavy load and heat build up that goes with it.  I try to
always plan for the worst and hope for the best.  You should see my
rigs.  The word "tank" comes to mind.  To make the point clear, I have a
Cooler Master HAF-932 case with those large fans.  The CPU cooler just
barely fits in the case, and the case is large. 


>> One, it is lightly loaded relative to what it can handle.  Two, it
>> will most likely handle heat better at those levels.  Third, it allows
>> for upgrades, hard drive additions etc without having to buy another
>> one.
> Just how does one calculate the amount of power a box will use?
> Processors proudly say "95W tdp", or whatever, but how much power does
> RAM use, or the motherboard, or SDDs, or HDDs?
>
> I'm anticipating building a new rig in the coming weeks/months
> (depending on how soon the motherboard makers start producing Ryzen MBs
> in quantity), and I'd be interested in getting an optimally sized PSU.
> Most of the time, my PC is just idling along, with sporadic bursts of
> activity like building libreoffice.
>
> So how do I work out the electricity consumption of all these
> components?


Usually I do it this way.  Whatever goes in the case and runs off the
P/S, I research how much power it uses.  CPU for example, I use that
wattage rating the manufacturer claims even tho it will likely be less
than that even while compiling and under heavy load.  Hard drives, same
thing.  Take the voltage, the current and multiply them to get wattage
if I can't find wattage itself.  Fans, add those up.  It takes a bit but
it gives a pretty good idea. 

There are websites to that can give you ideas and they also include some
wiggle room.  I've also been known to find someone who has the same mobo
and a close CPU model and either found what they say theirs pulls or I
just ask them outright.  That is usually some good info because it is
real world.


>> I hope that info will help.
> Thanks!
>
>> Dale

I might add.  My old rig had a Abit NF7 mobo.  It had a 2500+ single
core CPU.  It also had several hard drives, DVD and several fans.  It
pulled about 400 watts under load and not much better idle.  When I
built my new rig, I took a little info from that.  Thing is, things were
more efficient when I bought the parts for the new rig than it was for
my old rig.  My new rig, it pulls less than 200 watts.  Generally, it is
about 150 watts.  I'm getting that from both the UPS info and from a
power meter.  The UPS is pretty close.  Thing is, that includes a
router, modem and some little speakers as well.  The reason I add this,
a 500 watt power supply can power quite a lot of computer nowadays. 
Unless you have some high powered graphic cards and other power hogs,
really large P/Ss are not generally needed.  I could easily use a 300 to
350 watt P/S in my new rig and still have wiggle room and that power on
rush handled. 

Hope that helps.

Dale

:-)  :-)