If you are looking for Energy efficiency in your server build (and who isn’t?!), many Processor manufacturers, most notably Intel, have created lines of low power processors (LPP’s) designed to consume less electricity without greatly diminishing performance.  This post will cover what to look for when buying a low power processor and explain TDP, or Thermal Design Power, which is a key spec listed by manufacturers on their processors’ energy consumption.

Intel Xeon Low Power Processors

Intel lists their low power processors by designating an ‘L’ after the 4-digit product family number.  Below is where you would see it in the product description. 

As an added reference, it is printed on the chip as well.

In addition to Intel’s Low Power/”L” designation, processor manufacturers publish the processor’s energy requirements in TDP, which stands for Thermal Design Power.  All of TechMikeNY’s processors list the manufacturer’s published TDP:

What exactly is “TDP?”  It’s measured in Watts, so it must be the energy consumption of the processor.  Right?

Well, not exactly.  While TDP is based on the processor’s energy draw, it also factors in the energy needed to dissipate the heat that the processor creates.  In other words, a processor with a higher TDP most certainly draws more power, but it also requires more energy to cool, and that cooling factor is what goes into the TDP formula.  For example, take the processor listed above with TechMikeNY: it has a TDP of 65 Watts – but that 65 W is also considering the cooling system you need to dissipate its heat.  That’s why the TDP will generally be higher than the energy that the processor is pulling because it is accounting for the cooling of the heat as well.  In other words, a 65 Watt processor would not necessarily require a 65 Watt power supply.  

But a low TDP still means that the processor is a low power processor? 

There is a correlation, but because of the cooling factor, it is not a direct match between the power draw and the TDP.   In theory, a processor with a high TDP could be inefficiently designed – not using a lot of power for processing and calculations but requiring a lot of energy to dissipate its heat.  Conversely, a processor with a low TDP could be highly efficient and shed its heat effectively without needing additional power to do so.  

So how do I select a low power or energy efficient processor? 

A processor listed with a low TDP is likely a low power processor – just understand that it is not a plain vanilla answer.  At the same time, a processor with a very high TDP is not necessarily a high-performing processor.  While it’s true that more energy equals more processing power, much of that TDP wattage could be part of energy spent to cool.  Make sure that you have adequate cooling for a server running processors with high TDP.   

Final Thoughts

A processor’s TDP – while not an exact reflection of the processor’s power draw – is a good starting place to understand a processor’s efficiency and power consumption. (Keep in mind, processor manufacturers also use different criteria for measuring TDP, it’s not a 100% reliable metric (In fact, some feel that TDP has become a misleading, if not a downright flawed metric to look at when selecting a processor.)

Have a different take on TDP?  What criteria do you look for when selecting a low power processor?  We want to hear from you!  Email us at [email protected] or leave a comment below!