Re: [gentoo-user] Re: new machine : case + power

[Alan McKinnon]

On 24/09/2015 16:00, Volker Armin Hemmann wrote:
> Am 17.09.2015 um 05:38 schrieb james:
>> Philip Webb <purslow <at> ca.inter.net> writes:
>>
>>
>>>   150914 CPU : AMD X8 FX8370E 8-core 4,3 GHz 16 MB 32 nm 95 W
>>  I have 3) FX8350. Outstanding performance for the cost. Love them all.
>>
>>
>>
>>>   150914 Mobo : Gigabyte GA-970A-UD3P 970+SB950 DDR3 2000      :  119.99
>>>           2x PCI-Express x16 GLAN 6xSATA 6.0 Gb/s 4xUSB 3.0 14xUSB 2.0
>> I have (3) of the Ggiabyte 990A-UD3P mobos:: I love mine
>>
>> Very extensive wiring needs, plus you have to match the video card
>> power needs to the power supply. None of my older PS would fit the bill.
>> Also, there has been a quiet revolution in power supply. The efficiency
>> of the switching circuits will save you more money in the long run
>> and those electronics will deliver the cleanest power to your other
>> electronics. PS have ratings so look at the efficiency and oversizing a bit
>> from calculated loads is never a bad idea.
>> I would recommend to 'not go cheap' on the PS. Becuase
>> 4+ GHz can create some very localized heats, I put a 'water cooler'
>> on the chip that has hoses running to a radiaor bolted on the the main rear
>> fan of the Case. A wise investment at 4.3GHz. Air cooled CPUs are suspect
>> at those frequencies, particular if you like to compile  lots of code
>> or stress the all the cores at the same time.
>>
>>
>>
>>
>>>   150914 Memory : Kingston HyperX Fury 8 GB DDR3 1866 MHz CL10 :   68.99
>> I always max ram in lieu of SSD. I know you have a budget but max
>> ram is the single biggest item on performance and most things are
>> memory constrained on processing, ymmv.
>>
>> Every thing else look for bargains. Newegg is a great place to vett prices.
>>
>> Make sure your case has a big and quite fan to draw air across the HD. Most
>> new cases do. In all you buy, check the dB (sound level) especially if
>> you want a quite rig to sit near you. Make sure the UPS you have is
>> adequate and tested. Put a large light on the UPS. Yank the power cord
>> of the UPS to the wall and you should not see a flicker nor deeming
>> of the light of the bulb; thats a good UPS. UPS protects ALL your
>> electronics, but never printers as their power draw surges can easily
>> fry a smaller UPS.
>>
>> hth,
>> James
>>
>>
>>
>>
>>
> I have a 125w CPU and a R7 370 plus a shitload of HDDs and all those are
> quite happily fed by a 450W PSU. A pretty old 450W BeQuiet PSU.
>
> Go figure.
>
> What does my 600VA UPS says about this?
> 27% load at the moment.


That's all as expected. There's also this thing we called headroom:

As I said in an earlier mail, and got an earful for my trouble, a 125W
CPU does not draw 125W all the time and your 450W psu does not deliver
450W all the time. Your PSU is delivering about 125W or so average which
is what I expect from that hardware.

But computers are not nice well behaved LED bulbs that draw constant
power that never varies. The CPU ramps up to full S1 state, hard drives
spin up and that causes power draw to surge and spike. How much does it
need? Hard to give a definite answer but easily 5 or 6 times the
average, especially spinning up drives that spun down. You can see these
spikes on lab power meters, ones with screens and graphs. That's what
the headroom is for - how much extra power can be delivered in very
brief spikes (<100ms or so) when the hardware really needs it?

If the PSU is weak in this area and can't deliver the full power, the
load will still try to draw the current, and the voltage must drop to
compensate. Simple physics. Either way, your 450W PSU might not be up to
the job when push really comes to shove for your hardware.


-- 
Alan McKinnon
alan.mckinnon@×××××.com