2 Replies Latest reply on Sep 18, 2015 1:07 AM by Cesar Badilla

    DRAM RAPL Issue




      I am using a Xeon E5 1650 processor for my work and I have been trying to set the power limits for the DRAM through RAPL MSR's. There are no issues when I try to read the DRAM power consumption but

      when I write the power limits to to MSR_DRAM_POWER_LIMIT (0x618), there is no change in the DRAM power consumption.


      I tried to check the BIOS settings and I am attaching couple of images that I found. Apparently, there is an option DRAM RAPL MODE and it's value can be choses as ) Off 2) Mode 0 and 3) Mode 1.

      By default, the value was Mode 1. Can anybody tell me what exactly is the difference b/w these two modes. Also, what changes do I have to do to make the DRAM power limiting work?



        • 1. Re: DRAM RAPL Issue

          Hello kakarrot,


          You can get better support at:



          • 2. Re: DRAM RAPL Issue
            Cesar Badilla

            Hello kakarrot,


            The BIOS sets DDR RAPL mode though BIOS-to-Pcode Mailbox command.  In this case you may Set DRAM only, the power consumption of the main memory.


            In  regards to DRAM RAPL modes you have two options: DRAM RAPL MODE0=DRAM power from pure activity based estimation and  DRAM RAPL MODE1= DRAM power from scaling activity-based estimation to match DDR VR total power (based on VR12 IOUT register)


            Caesar B.