https://community.intel.com/t5/Software-Tuning-Performance/what-is-the-control-register-address-for-setting-DVFS-values/m-p/932152#M1546 <DIV class="jive-rendered-content"> <P>Hi ,</P> <P>May I know which system register (I am using a core 2 duo&nbsp; E8400) should be used to control the possible voltage/freq settings for DVFS. I am not trying to over clock the cpu. I am trying to select one of the pairs of available voltage/freq combinations. ACPI drivers do it save power during idle periods. I went through manual vol 2 and 3 and was able to read performance registers using rdmsr/wrmsr commands. But, I was not able to find the address of the control register that can control the DVFS settings.</P> <P style="min-height: 8pt; height: 8pt; padding: 0px;">&nbsp;</P> <P>Thanks,</P> <P>Nanda</P> </DIV> Sun, 08 Dec 2013 21:07:46 GMT Nanda_K_ 2013-12-08T21:07:46Z https://community.intel.com/t5/Software-Tuning-Performance/what-is-the-control-register-address-for-setting-DVFS-values/m-p/932152#M1546 <DIV class="jive-rendered-content"> <P>Hi ,</P> <P>May I know which system register (I am using a core 2 duo&nbsp; E8400) should be used to control the possible voltage/freq settings for DVFS. I am not trying to over clock the cpu. I am trying to select one of the pairs of available voltage/freq combinations. ACPI drivers do it save power during idle periods. I went through manual vol 2 and 3 and was able to read performance registers using rdmsr/wrmsr commands. But, I was not able to find the address of the control register that can control the DVFS settings.</P> <P style="min-height: 8pt; height: 8pt; padding: 0px;">&nbsp;</P> <P>Thanks,</P> <P>Nanda</P> </DIV> Sun, 08 Dec 2013 21:07:46 GMT https://community.intel.com/t5/Software-Tuning-Performance/what-is-the-control-register-address-for-setting-DVFS-values/m-p/932152#M1546 Nanda_K_ 2013-12-08T21:07:46Z https://community.intel.com/t5/Software-Tuning-Performance/what-is-the-control-register-address-for-setting-DVFS-values/m-p/932153#M1547 <P>I believe the register&nbsp;IA32_PERF_CTL MSR (0x199) is the one to which you can write the value of a particular P state frequency and voltage id.</P> Sun, 08 Dec 2013 23:07:34 GMT https://community.intel.com/t5/Software-Tuning-Performance/what-is-the-control-register-address-for-setting-DVFS-values/m-p/932153#M1547 gokussj9 2013-12-08T23:07:34Z