[mythtv-users] Low Power System

[Stephen Worthington]

On Mon, 6 Mar 2017 16:56:24 +1000, you wrote:

>On 06/03/17 13:54, James Linder wrote:
>>
>>
>> On 6/3/17 10:28 am, mythtv-users-request at mythtv.org wrote:
>>>> I have been a MythTV user for over 10 years but haven't kept up with
>>>> the changing hardware.  My last iteration was a Zotac Atom 230
>>>> combined front/backend which unfortunately died recently.
>>>>
>>>> We are moving off-grid (solar only) soon so I am looking for a
>>>> low-power system to watch TV/videos and listen to mythmusic. That's
>>>> basically all we use the Mythbox for.  Tuner is a networked HDHomerun
>>>> and there is ~2TB of data (recordings, videos, music).
>>>>
>>>> Should I be looking at the latest generation of Zotac motherboards or
>>>> am I better off looking at a laptop?  I could probably squeeze
>>>> everything into a laptop if it had dual HDD slots.
>>>>
>>>> All suggestions welcome.
>>>>
>>>>
>>> I've just updated one of my MythTv frontends using an ASRock J3710-ITX
>>> mini-itx board. This has an Intel Quad-Core Pentium Processor J3710built
>>> onto the board and has a power usage of < 6 Watts. It has optical audio
>>> out for surround sound amps etc. There is a Celeron version which is
>>> slightly cheaper. Teamed with a cheap SSD SATA disk or USB stick to boot
>>> from it work well with SD and HD. The video is hardware decoded in the
>>> CPU's graphics chip. Using a Fedora 25 installation with the VAAPI
>>> drivers uses about 15% of the CPU's watching full HD and is quick with
>>> the MythTv menu's etc. Seems to work well so far.
>> What I've found is
>>
>> I use a NUC with a decent processor (i3 v6 or i5)
>> The box is not rated for low power in particular but running mythbackend
>> on a flash disk actual power usage is a couple off watts only.
>> if you use flash then 2 stuff:
>>     partition your flash such that (say) 20% is unpartitioned. That
>> gives a stock of sectors that trim can claim as sectors get worn out
>>     deal with mysql logging. The log will wear out your flash in a year.
>>     I run trim as a daily cron task. Recomendation is to not put it in
>> fstab.
>>     BTW a 2.5" 1T spinning disc adds little to power, but makes life
>> much easier
>>
>> James
>
>Thanks James, I actually do most of that now, with the exception that 
>trim is in fstab - any sources on why not?
>
>Do you know of any NUCs that could fit two 2.5" or perhaps 1 3.5" and a 
>boot disk?  Probably starting to creep the power up now.
>
>I assume NUC's would typically use a power brick which should be more 
>efficient than standard ATX power supply. I may also be able to run it 
>straight from our battery bank instead of using an inverter.
>
>I will also be investigating spindown, ACPI wakeup & Mythwelcome, etc..
>
>Thanks,

Unless a power brick is designed for a laptop, it is likely to be less
efficient than a good ATX power supply.  The problem with low power
ATX power supplies is that they do not exist below about 250-300
watts.  If you buy a quality ATX power supply with 80 Plus
certification, it will be 80-95% efficient when running in the within
a wide band of its power output range, depending on the certification
level.

Non-laptop power bricks often run very hot ie they are really
inefficient.  But if they are only rated at say 70 watts and supplying
that, then they can be losing say 35 watts to inefficiency and still
be using less power overall (105 W) than a 300 W ATX supply might use
running outside its normal range of operation to supply only 70 W.

Most laptop power bricks seem to be reasonably well designed, but I
have come across one that always draws 15 W even when not plugged into
a laptop.

If you really want low power, with lots of capability, a laptop seems
to be a good way to go.  They really are designed for low power
operation.