[mythtv-users] Number of Cores v. Clock

[George Galt]

On Sun, Jun 13, 2010 at 10:26 PM, Christopher Kerr
<mythtv at theseekerr.com> wrote:
> 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
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Thanks.  I already have a VDPAU card that will be staying with the
system.  This is a refresh of just the CPU/Motherboard, so I was
mostly interested in the impact of cores/clocks on backend tasks.
After further research it seems the i5 750 is the chip of choice, so
I'll go that way.  Thanks for the help.

George