[mythtv-users] Number of Cores v. Clock

[Christopher Kerr]

On Mon, Jun 14, 2010 at 12:00 PM, George Galt <george.galt at gmail.com> wrote:
> i am working on an unexpected refresh of my myth backend/frontend and
> i have been staring at Newegg for several hour without enlightenment.
> The question is, do I go for more cores (6) with a lower clock or
> fewer cores at a higher clock?  The AMD six-core is here
> http://www.newegg.com/Product/Product.aspx?Item=N82E16819103851  there
> are several AMD and Intel quad-cores with higher clocks.  This system
> will be used exclusively for MythTV, so i am really focused on the
> impact of clocks v. cores on MythTV.  Thanks.
>
> George

Frankly, 2.8GHz is probably as fast as you need for most things anyway.

For a FE/BE, assuming capture from a digital source, CPU time is
mostly spent on:

- Decoding content (negligible for MPEG2, significant for H264, almost
nothing if you're using VDPAU)
- Deinterlacing (significant unless you're using VDPAU. Of course, you
really should be since it does such a good job ;o)
- Commercial flagging (seems to be resolution dependent? Anyhow, for
real time HD commflagging, you're probably looking at one core per
simultaneous recording, but I'm not sure. I can manage at least 5 SD
shows simultaneously on my 2.8GHz quad, but I don't do much HD)
- Transcoding. If you don't do any transcoding, this is fairly
irrelevant, but it's one area that really benefits from higher clocks.
OTOH, since it ties up a whole core for a while, it can be handy to
have the extra cores....

Also note that the Intel chips are faster clock for clock, so they're
harder to compare on paper. The bang-for-buck chips are the i5 750 and
the i7 930. See AnandTech for excellent reviews.

At the end of the day? I'd buy a VDPAU capable card and a quad core,
unless you're dealing with a great many simultaneous recordings.

- Chris