I am building a new system to be on 24/7. As such, when the system is idling, I want its power consumption as low as possible. To achieve this, I am planning on underclocking / undervolting the processor as much as I can.
I am looking at getting one of AMDs 45W TDP energy efficient X2s.
There are three versions; a 2.1Ghz (4050), 2.3Ghz (4450) and 2.5Ghz (4850).
What I want to know is if I go for the gruntiest one (4850) to give more power when needed, will I be able to under volt / underclock it to achieve the same idle power consumption figures as the slowest processor (4050)?
I have heard it suggested that they are all exactly the same processor and the 4850s are just the ones which stay stable at higher clock multipliers. If this is the case, I would imagine that I could undervolt them all to the same level. Is this right?
When those CPUs idle, with Cool'nQuiet on presumed, they all operate at 1000MHz with 5x multiplier. The only difference among these CPUs is maximum multiplier. 4850e has the highest multiplier (12.5x). The ability to under volt/ underclock is within the limit of the motherboard. You can get a 5400+BE to operate like 4x50e if you want, and that's my suggestion to you since all these CPUs are just so cheap that I don't really care about the price difference anymore.