One of the big problems with servers and data centers is that they have a power budget to adhere to. We know that Bulldozer is designed for low power use and comes with a relatively advanced Turbo Core function, but now head of servers at AMD John Fruehe says that it can limit TDP when needed.
TDP stands for Thermal Design Power and is a guidelinie for how powerful the cooling have to be, and how much a circuit can consume at worst case scenario. AMD’s Valencia will sport 4-8 cores and Interlagos 8-16 cores, and both will have a nice feature for limiting the TDP.
The function is called TDP Power Cap and enables you to lower the TDP in BIOS in steps of 1W. If you get a 105W TDP processor you can easily lower the TDP to 90W. John Fruehe explains how TDP Power Cap works in an forum post:
”Keep in mind that with power capping, TDP over rules the clock speed in some cases.
Let’s say you buy a 105W TDP processor and set it at 90W. For some workloads you might still get base clock speed, and possibly even boost.
But if you set it at 90 and your workload needs 95W to reach full clock speed, you might end up with a top clock speed that is slightly lower than base.
The feature is for customers that value power efficiency over clock speed and performance. Think of web, cloud and other workloads where lots of low power cores are the norm” ~ John Fruehe
Different types of applications and software load the processor differently, so even though the threshold has been restricted in BIOS, Turbo Core will assist you at times, while in other cases you will run with a frequency lower than the base frequency.
TDP Power Cap is more or less a very advanced form of undervolting with official support from AMD, but you will not be able to turn up the TDP for overclocking. AMD will continue to build processors at different TDPs from factory, but TDP Power Cap is just a function to make sure you can adjust the pwoer consumption and make some choices easier for buyers.
A lot of the Bulldozer architecture will be controlled by TDP, among them Turbo Core since the processor has a dedicated piece of silicon to keep track of the power, which is why Bulldozer will be able to go into Turbo even though all cores are loaded as long as the TDP keeps. It is still unclear if we will see this function in the retail channel.