Diggin' technology every day

June 29, 2011

Adjust CPU power in 1 watt increments

Filed under: General — Tags: — Nate @ 2:09 pm

Saw this over at the AMD blog recently, certainly sounds pretty neat, the ability to control the power usage of your CPU on a per-watt basis, which is significantly more effective than current power limiting strategies available today.

Well, let’s say that you have a maximum power draw on your fully configured server of 300W, and you have 42 slots in your server.  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.

No mention on whether or not the processor will turn off cores once you hit certain thresholds (say you reduce a 80W 12-core cpu to 60W of power, it may be better to run fewer cores with higher clock speeds than more cores on lower clock speeds depending on the workload).


  1. We do have a feature called AMD Core Select that will allow you to shut off individual cores if needed. But with TDP capping you will reduce clock speed if you ran the 80W processor at 60W. Depending on the power profile of your application you may be able to still hit the same clock speed in that scenario, but if that power associated with that clock speed was higher than 60W, you would see a lower clock speed.

    Comment by John Fruehe — June 29, 2011 @ 9:29 pm

  2. Thanks for the post!

    I did a little bit of searching on AMD Core select, and it seems like it’s not a dynamic process but more of a static configuration where you select the cores in advance and then it cannot be changed without downtime?

    Or is it dynamic – ability to turn cpu cores on and off while things are running? I can’t find much information on this feature other than passing references.

    Comment by Nate — July 8, 2011 @ 8:40 am

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