14-32 Vol. 3B

POWER AND THERMAL MANAGEMENT

MSR_RAPL_POWER_UNIT (Figure 14-31) provides the following information across all RAPL domains:

•

Power Units (bits 3:0): Power related information (in Watts) is based on the multiplier, 1/ 2^PU; where PU is 
an unsigned integer represented by bits 3:0. Default value is 0011b, indicating power unit is in 1/8 Watts 
increment.

•

Energy Status Units (bits 12:8): Energy related information (in Joules) is based on the multiplier, 1/2^ESU; 
where ESU is an unsigned integer represented by bits 12:8. Default value is 10000b, indicating energy status 
unit is in 15.3 micro-Joules increment.

•

Time Units (bits 19:16): Time related information (in Seconds) is based on the multiplier, 1/ 2^TU; where TU 
is an unsigned integer represented by bits 19:16. Default value is 1010b, indicating time unit is in 976 micro-
seconds increment.

14.9.2 

RAPL Domains and Platform Specificity

The specific RAPL domains available in a platform vary across product segments. Platforms targeting the client 
segment support the following RAPL domain hierarchy:

•

Package

•

Two power planes: PP0 and PP1 (PP1 may reflect to uncore devices)

Platforms targeting the server segment support the following RAPL domain hierarchy:

•

Package

•

Power plane: PP0

•

DRAM

Each level of the RAPL hierarchy provides a respective set of RAPL interface MSRs. Table 14-4 lists the RAPL MSR 
interfaces available for each RAPL domain. The power limit MSR of each RAPL domain is located at offset 0 relative 
to an MSR base address which is non-architectural (see Chapter 35). The energy status MSR of each domain is 
located at offset 1 relative to the MSR base address of respective domain.

Figure 14-31.  MSR_RAPL_POWER_UNIT Register 

Table 14-4.  RAPL MSR Interfaces and RAPL Domains

 Domain

 Power Limit

(Offset 0)

 Energy Status (Offset 

1)

 Policy

(Offset 2)

 Perf Status

(Offset 3)

 Power Info

(Offset 4)

PKG

MSR_PKG_POWER_

LIMIT

MSR_PKG_ENERGY_STA

TUS

RESERVED

MSR_PKG_PERF_STATUS

MSR_PKG_POWER_I

NFO

DRAM

MSR_DRAM_POWER

_LIMIT

MSR_DRAM_ENERGY_S

TATUS

RESERVED

MSR_DRAM_PERF_STATUS MSR_DRAM_POWER

_INFO

PP0

MSR_PP0_POWER_

LIMIT

MSR_PP0_ENERGY_STA

TUS

MSR_PP0_POLICY MSR_PP0_PERF_STATUS

RESERVED

63

0

Reserved

13

3

4

7

8

12

15

19

20

Time units

Energy status units
Power units 

16