[mythtv-users] Powersaving AMD CPU for my system wanted.

[Raymond Wagner]

On 12/29/2011 16:46, M D wrote:
>> If you say this one is also ok, i will go with that one,
>> wich leaves me with the ram to choose. Are there any things
>> i need to know when buying ram? And is my mentioned capacity
>> of about 1-2 gb the right choice ?
> It has 8 Gb of ram and I find the swap and cache used regularly.
> For example, top (via ssh) reports that currently most of the
> memory is used, 6.5+ gig is cached and 295mb is used in the swap

Well of course 6.5+GB is cached.  The cache is a temporary copy of data 
that exists on disk, and allows reads and writes to return must faster 
than if they had to go immediately to disk.  The cache will use up every 
single last bit of memory you have, and will be automatically flushed 
out as you have other need for memory.  295MB of swap used is a bit 
disconcerting, but likely nothing you need to worry about.  2GB of 
memory is a good solid minimum for a combination frontend/backend.

> As for the video .... I always wonder why people do not use the
> onboard video and sound, but then add in another video card (an
> additional power draw) for machines that are designed for power
> saving.

Onboard audio and video is great, when it's an option.  Back when nVidia 
still made integrated video, that was often the recommended option.  
Sadly, Intel and AMD are pushing hard for video integrated on the CPU, 
and so nVidia has abandoned that market entirely.  The only products 
remaining are fairly expensive ones using mobile nVidia chips.

Integrated Intel and AMD video work fine on OSX and Windows, where there 
is a very large market giving reason to develop capable, reliable 
drivers.  On Linux, nVidia still has by far the best support of the 
three, meaning nVidia graphics are still the recommended option, which 
in turn requires a discrete card.

Intel hardware can be made to work in most cases, but have their share 
of conflicts with Myth's video output code, and lack some of the extra 
niceties nVidia provides.  AMD support is rapidly getting better, but 
they have a long standing tradition of complete garbage drivers during 
the ATI days that they have to recover from.

> I went with a higher powered CPU and on-board video with the intention
> of using this box as a media server for other backends.  It is safe to
> say you need to get the most powerful processor that you can live with
> on a power-consumption basis.  However, I think the MB and power
> supply and hard drive are also critical in that regard too.

A high end multi-core processor will really only help you if you're 
doing Bluray playback, or doing a lot of transcoding to H264.  Most 
broadcast content will be relatively moderate bitrate, and usually only 
in a format that allows single threaded playback.  A dual core processor 
at 2.5-3GHz is sufficient for most needs.

With everything being moved into the CPU and out of the chipset, the 
motherboard itself is consuming less and less power.  Right now, all it 
tends to drive are the accessory buses, like USB, SATA, and sometimes 
PCI-express.  It's not going to draw much on its own.  Hard drives 
require a lot of power, when they're running, but there is no need for 
them to be running most of the time.  Modern drives use less than 1W 
when spun down, 6-10W spun up, and 15-25W spinning up.

The power supply is a big, and very misunderstood, issue.  Without a 
high end graphics card, PCs really don't draw that much power.  A nice 
dual core processor, motherboard, and memory might draw 80W under full 
load.  A discrete graphics card capable of anything MythTV might want 
for will come in under 50W.  Depending on how many hard drives and tuner 
cards you stuff in the box, you're looking at a maximum possible power 
draw somewhere under 200W, and yet its damn near impossible to find ones 
that small.  Everyone is pushing 80Plus ratings, but 80Plus only rates 
power supplies down to 20% of rated output.  Efficiency below 20% is 
unmeasured, yet people buy 400-600W power supplies for HTPCs, not 
realizing their idle consumption is going to be under 50W and peak load 
might be three times that.