[mythtv-users] Quick opinions

John Drescher drescherjm at gmail.com
Mon Jun 1 14:32:22 UTC 2009


On Mon, Jun 1, 2009 at 9:51 AM, belcampo <belcampo at zonnet.nl> wrote:
> John Drescher wrote:
>>>
>>> I too have been looking at these two processors to go with a asus
>>> M3N-H/HDMI
>>> motherboard.
>>> As my system is going to be running 24/7 mainly at idle, looking at the
>>> power consumption it appears looking here LINK that the 5050e uses 4watts
>>> less than the X2 5400+ at idle, then if we look here LINK it shows that
>>> the
>>> 7750 uses 7.8watts more than the 5400+ at idle therefore I have assumed
>>> that
>>> the 7750 uses 11.8watts more than the 5050e at idle.
>>> On a UK tariff of approx 13p Kwh that works out at a extra annual cost of
>>> 13.44 to run the 7750
>>> However if I am unable to get VDPAU working satisfactorily on that board
>>> I
>>> am unsure whether the 5050e is powerful enough for BBC HD and ITV HD.
>>>
>>
>> The 2.7 kuma is supposed to be 10% to 30% clock for clock more
>> efficient than the older series. Also the kuma X2 is actually a 4 core
>> chip (made in the same batch as Phenom 1 chips) but with 2 of its
>> cores disabled yet still partially powered so this will explain part
>> of the 11W idle difference.
>>
>> BTW, one thing you can do to reduce the idle power draw of a cpu is to
>> lower its voltage at idle. This underclocking / undervolting is
>> basically what AMD does to create the energy efficient desktop chips
>> since they use the exact same design and process and are made in the
>> same batch / wafer as the non energy efficient cpus. I can go more
>> into this if it sounds confusing..
>
> If I understand correct, there is 1 physical designed/manufactured CPU where
> 1 is sold/configured to work at say 100%V and the energy-efficient one to
> work on 80%V with the same horsepower as a result ??
>>

Its hard to explain this fully without taking a lot of time. In the
process of producing chips on a wafer flaws are introduced such that
no chips produced are perfect. Each core is designed to be identical
but because of these flaws they do not all operate at the design
frequency (actually very few of them do). In the process the ones
produced in the center of the wafer are generally better than the ones
farther out on the same die. The better ones will either clock higher
or run at a lower voltage than the lesser ones.

So what I am saying is that the energy efficient cpus are taken from
the same group of better chips and these are the same as the high end
chip of the same stepping. However the manufacturer instead programs
the chip p-states to cut out 2 or more of the high p-states such that
the chip will fit in a lower power envelope. What I am also saying is
that if you wanted you could easily take a high end chip of the same
stepping and do the same if you wanted or tweak the process. I mean
you can get the low power idle and not sacrifice frequency at full
load.

John


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