Vol. 3B 17-61

DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES

17.17.5.4   Associating Threads with CAT/CDP Classes of Service 

Threads are associated with Classes of Service (CLOS) via the per-logical-processor IA32_PQR_ASSOC MSR. The 
same COS concept applies to both CAT and CDP (for instance, COS[5] means the same thing whether CAT or CDP 
is in use, and the COS has associated resource usage constraint attributes including cache capacity masks). The 
mapping of COS to mask MSRs does change when CDP is enabled, according to the following guidelines:

•

In CAT-only Mode - one set of bitmasks in one mask MSR control both code and data.
— Each COS number map 1:1 with a capacity mask on the applicable resource (e.g., L3 cache).

•

When CDP is enabled, 
— Two mask sets exist for each COS number, one for code, one for data. 
— Masks for code/data are interleaved in the MSR address space (see Table 17-20).