[mythtv-users] Cpu and power management

Michael T. Dean mtdean at thirdcontact.com
Mon Aug 4 16:26:35 UTC 2008

On 08/04/2008 11:44 AM, Kevin Kuphal wrote:
> On Mon, Aug 4, 2008 at 10:40 AM, wouter lists wrote:
>> My htpc died last night, so it's time for a new one.
>> As the energy prices keep rising, it's time to invest in a power
>> efficient CPU. What CPU has the lowest power consumption? I'm gonna
>> stay with Intel or AMD. High definition would be nice but is not
>> required.

Intel Core 2 is a more power efficient CPU than the AMD Athlon 64-type 
CPU's.  However, when you go about adding in other things (like, 
especially, chipsets and mobo's and RAM and ...) you may find that 
buying the most power-efficient CPU is like choosing to buy one house 
because you happened to notice a single compact fluorescent lamp in it.  
Chances are that one bulb is a small enough part of total power usage 
that its effect is negligible.

Modern CPU's aren't very power-hungry compared to older designs.  In a 
P4 - or Athlon-XP-based system, the CPU power usage is likely to be a 
much greater percentage of total power usage.

Best bet is to build two systems in the exact configuration you want and 
measure at-the-wall usage of both (using, for example, a Kill-a-Watt).  
While I know that's not really possible, I'd say you can't go wrong with 
any Athlon 64-type or Core 2 system.

>> My local pc store told me that it's better to buy powerfull
>> powersupply, eg 700Watt output. According to him it handles much
>> butter the output then a cheap 400Watt powersupply. Is this correct?
> Check out the 80plus program
> http://www.80plus.org/

And the PSU is likely to have a much greater effect on overall 
at-the-wall power usage than any choice between Intel vs AMD.  So, 
Kevin's advice is probably the best advice you can get.

Note, also, that it's important to have a PSU matched to the system's 
actual power usage.  Some PSU's operate at extremely low efficiency when 
not at "ideal" load.

I recently had a PSU blow up and--fortunately--it did so on a day when 
an 80-plus PSU was on a very good sale (making as cheap as any 
similar-quality non-80-plus PSU).  Since getting that PSU, I'm a big 
believer in 80-plus rated PSU's.  Mine (and Antec Earthwatts 430W PSU) 
runs at 80-plus (meaning 80% efficiency or better) from 20% to 100% 
load.  I'm guessing I'm running closer to the 20% load than to the 100% 


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