Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
18-130 Vol. 3
DEBUGGING AND PERFORMANCE MONITORING
Additional performance monitoring capabilities and facilities unique to 64-bit Intel
Xeon processor MP with an L3 cache are described in this section. The facility for
monitoring events consists of a set of dedicated model-specific registers (MSRs),
each dedicated to a specific event. Programming of these MSRs requires using
RDMSR/WRMSR instructions with 64-bit values.
The lower 32-bits of the MSRs at addresses 107CC through 107D3 are treated as 32
bit performance counter registers. These performance counters can be accessed
using RDPMC instruction with the index starting from 18 through 25. The EDX
register returns zero when reading these 8 PMCs.
The performance monitoring capabilities consist of four events. These are:
IBUSQ event — This event detects the occurrence of micro-architectural
conditions related to the iBUSQ unit. It provides two MSRs: MSR_IFSB_IBUSQ0
and MSR_IFSB_IBUSQ1. Configure sub-event qualification and enable/disable
functions using the high 32 bits of these MSRs. The low 32 bits act as a 32-bit
event counter. Counting starts after software writes a non-zero value to one or
more of the upper 32 bits. See Figure 18-49.
Figure 18-48. Block Diagram of 64-bit Intel Xeon Processor MP with 8-MByte L3
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