Am Mon, 20 Mar 2017 18:16:55 +0000 schrieb Alan Mackenzie <a...@muc.de>:
> 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). > > > 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 think that is pretty much well documented somewhere. HDDs use much more power during spinup, after that they should be somewhere around 10 watts - depending whether you access them or not. SSDs have no spinup but also vary in power draw if accessed or not accessed. But whatever you do, they should stay far below HDDs. Take care of the PSU efficiency. Most are at 80%. The rest of the watts is just converted to heat. Similar with CPUs, tho most of the watts are converted to heat. Actually, CPUs draw more power than the TDP value, especially during peaks (for example, when turbo boost activates). A system producing less heat automatically uses less watts. For you CPU I'd suggest to undervolt it (start with 0.1 to 0.2 volts), it should reduce heat by a good degree, and thus also power drawn. I undervolted my i5 2500k by 0.15 volts (offset mode), and instead raised the turbo multiplier from 37 to 40, plus added a better cooler. The result is: No more thermal throttling, temperature is 10-20°C lower, idle temp is much lower. I didn't measure power drawn but expect it to be some watts lower which I expect to improve my PSU live. > 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. I wouldn't call that a sporadic burst... Building LO is a heavy long-time job in terms of CPU cycles and power drawn. And it forces heavy duty on all components at once: HDD, RAM, CPU. No no, not sporadic... ;-) > So how do I work out the electricity consumption of all these > components? Look at the specs of each component (peak values), add some safety, plan for undervolting (CPU, maybe also RAM), and buy a PSU with efficiency above 80%. -- Regards, Kai Replies to list-only preferred.
