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MPAMCFG_MBW_MAX, MPAM Memory Bandwidth Maximum Partition Configuration Register

The MPAMCFG_MBW_MAX characteristics are:


MPAMCFG_MBW_MAX is a 32-bit read-write register that controls the maximum fraction of memory bandwidth that the PARTID selected by MPAMCFG_PART_SEL is permitted to use. MPAMCFG_MBW_MAX_s controls maximum bandwidth for the Secure PARTID selected by the Secure instance of MPAMCFG_PART_SEL. MPAMCFG_MBW_MAX_ns controls the maximum bandwidth for the Non-secure PARTID selected by the Non-secure instance of MPAMCFG_PART_SEL.

A PARTID that has used more than MAX is given no access to additional bandwidth if HARDLIM == 1 or is given additional bandwidth only if there are no requests from PARTIDs that have not exceeded their MAX if HARDLIM == 0.



This register is present only when MPAMF_IDR.HAS_MBW_PART == 1 and MPAMF_MBW_IDR.HAS_MAX == 1. Otherwise, direct accesses to MPAMCFG_MBW_MAX are RES0.


MPAMCFG_MBW_MAX is a 32-bit register.

Field descriptions

The MPAMCFG_MBW_MAX bit assignments are:


HARDLIM, bit [31]

Hard bandwidth limiting.


When MAX bandwidth is exceeded, the partition contends with a low preference for downstream bandwidth beyond its maximum bandwidth.


When MAX bandwidth is exceeded, the partition does not be use any more bandwidth until its memory bandwidth measurement falls below the maximum limit.

Bits [30:16]

Reserved, RES0.

MAX, bits [15:0]

Memory maximum bandwidth allocated to the partition selected by MPAMCFG_PART_SEL. MAX is in fixed-point fraction format. The fraction represents the portion of the total memory bandwidth capacity through the controlled component that the PARTID is permitted to allocate.

The implemented width of the fixed-point fraction is given in MPAMF_MBW_IDR.BWA_WD. Unimplemented bits are RAZ/WI. The implemented bits of the MAX field are always to the left of the field. For example, if BWA_WD = 3, the implemented bits are MPAMCFG_MBW_MAX[15:13] and MPAMCFG_MBW_MAX[12:0] are unimplemented.

The fixed-point fraction MAX is less than 1. The implied binary point is between bits 15 and 16. This representation has as the largest fraction of the cache that can be represented in an implementation with w implemented bits is 1 - 1/w.

Accessing the MPAMCFG_MBW_MAX

This register is within the MPAM feature page memory frames. In a system that supports Secure and Non-secure memory maps, there must be both Secure and Non-secure MPAM feature pages.

MPAMCFG_MBW_MAX_s must be accessible from the Secure MPAM feature page. MPAMCFG_MBW_MAX_ns must be accessible from the Non-secure MPAM feature page.

MPAMCFG_MBW_MAX_s and MPAMCFG_MBW_MAX_ns must be separate registers. The Secure instance (MPAMCFG_MBW_MAX_s) accesses the memory maximum bandwidth partitioning used for Secure PARTIDs, and the Non-secure instance (MPAMCFG_MBW_MAX_ns) accesses the memory maximum bandwidth partitioning used for Non-secure PARTIDs.

MPAMCFG_MBW_MAX can be accessed through the memory-mapped interfaces:


Accesses on this interface are RW.


Accesses on this interface are RW.