[mythtv-users] power management on combined and backend

[Stephen Worthington]

On Thu, 3 May 2018 07:43:33 -0400, you wrote:

>I have an i7 920 and an MSI X58 motherboard, two drives, 1 TB (mostly OS
>and some /storage) and one 2 TB (/storage2), and a GTX 780.  I also have a
>HD-PVR.
>
>I am trying to get my power consumption down on my combined backend and
>frontend.  I have set power settings in bios and the nvidia control panel
>to use on demand. In powertop, I can see that the cpus ghz is lower on all
>cores.   In powertop, I noticed nvidia was at 100% so I set /*sys*/bus/*pci*
>/*devices*/(insert pci address of nvidia here) to auto from on.  When I
>restarted powertop, nvidia was no longer showing "bad".   Under device
>stats, pci and usb show 100%.  I believe these also need to be set via
>/sys/bus/pci/devices?
>
>I'm not sure what if anything I should change on the hard drives.
>
>Initially I had 100 watts at the wall, with no playback or recording.  When
>I am watching tv it goes to about 150 watts. I have not tested since
>changing the nvidia /sys/bus/pci/devices.
>
> I was curious what others do with power management?

The best way to get lower power use is to use the most modern
hardware.  Every time I have updated my PC, even though the new
hardware is faster and bigger, the power consumption goes down.  My
old Athlon Windows box used to use 220 W or so when in use, then the
Core2 Duo with 4 Gibytes of RAM used around 180 W, and the latest
version with AMD FX-8350 8 core 4 GHz processor and 16 Gibytes of RAM
uses only around 140 W.

The video card can be using as much as the rest of the PC if you run
it in a full out gaming 3D mode, but if you buy the cheapest type of
video card that only does what is needed for TV (which is H.264
decoding at present), and is incapable of running modern games, then
you can get rather lower power use there.  Of course, if you want to
handle 4K video, then you probably want a rather better video card
that does H.265 decoding, and those have tended to use more power. But
the recent bottom end cards from Nvidia seem to have H.265 4K
capability without such large power hunger - they are available in
fanless versions.

If you want your drives to shut down automatically after a certain
idle time, then the best way to do that is to do it using the settings
on the drives themselves.  A lot of drives can do this now, but only
some come pre-programmed to do it.  You may need to use the
manufacturer's utility to change those settings, so the drive may need
to be put on a Windows PC to do that.  For the older WD Green drives,
the idle3ctl Linux utility can change the settings, but I am not sure
about the latest WD drives.  The downside of have the drives stop
rotating is that they take some time to start again.  MythTV is fine
with that for recordings, but you do notice it if you start playback
of a recording on a drive that has to start up first.  And the system
drive should never be set to do idle shutdowns - it will wear itself
out shutting down and starting up all the time.

I generally pay a little bit more for my power supplies to get higher
efficiency there.  The 80 Plus Gold specification or better is
recommended.  And power supplies that meet that spec also seem to be
better built and last longer.  Do not buy a power supply that is too
large for the PC - that can mean that the PC consumes its power most
of the time at the bottom of the power supply's output range, where it
is out of the region where the power supply works efficiently.  A 1000
W power supply in a PC that typically draws only 100 W will be wasting
a fair bit of power, even if it is an 80 Plus Gold model.

Getting 100 watts at the wall is pretty good.  Here in New Zealand,
with electricity at about NZ$0.25 per kW/h, that equates to NZ$219.15
per year.  Which would be about US$151.

But you will be using rather more than 150 W on playback, as running
the TV will typically be taking more than 150 W itself, on top of the
PC.

MythTV does have the option to have the PC shut down to a sleep state
between recordings.  Getting it to work properly depends on how good
the BIOS is at waking up again at the time it was told to.  Some
BIOSes do it well, and some not at all.  I have never tried it myself,
but it used to be popular a few years ago.