AMD unveils custom TDP technology for Bulldozer

AMD has confirmed a new feature for its Opteron processors based on the Bulldozer architecture: the ability to set a custom Thermal Design Power to get the most out of your rack's energy allowance.

Revealed by AMD's John Fruehe earlier this week and confirmed at a Bulldozer-themed press event today, TDP Power Cap is a technology that will be introduced the Interlagos and Valencia Opteron processor lines in order for datacentre customers to make better use of their power allowance.

Today's processors come with a Thermal Design Power, which is a rating of maximum energy draw and heat output. A high-end processor may have a TDP of 150W, for example. AMD's TDP Power Cap is a software-configurable option to push the TDP downwards, forcing the CPU into a lower-power configuration in order to save energy.

"Let’s say that you have a maximum power draw on your fully configured server of 300W, and you have 42 slots in your rack," Fruehe explains on the AMD Business Blog. "The simple math says that you have 12.6KW of power load that you need to be able to support. Now, if your power budget only allows you to bring 12KW to the rack, you essentially have 2 slots that need to be left open in the rack because you can only support 40 and not 42 servers. But, by utilizing a custom TDP, you could drop the max power that some servers could draw, bringing you in under the limit of 12KW and still getting 42 servers in the rack.

"Best of all, if your workload does not exceed the new modulated power limit, you can still get top speed because you aren’t locking out the top P-state just to reach a power level," Fruehe claims.

The new TDP Power Cap system builds on the company's existing product, which allows users to limit the processor's P-states in order to cut power consumption by preventing the chip from ever using its maximum performance settings. The new system, however, could potentially allow for chips to run at impressive speeds despite a low power draw, depending on workload.

So far, the technology is only destined for the server market. "I'm not sure how or if it's being productised that way in desktop products," Fruehe explains. "The fact that they have Overdrive might negate the need for it," he added, referring to his company's technology for automatically altering the performance of the processor based on load.

The introduction of the new TDP Power Cap with the Bulldozer architecture won't spell the end to similar products being offered with different TDPs, however. "The different power bands guarantee that you will achieve that clock speed at that power limit," Fruehe explains. "The HE and EE power bands will give customers a guarantee of performance, TDP capping will give customers flexibility, but the performance outcome is based on the actual demand for the workload, which can vary."