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

Table Of Contents
Vol. 3 A-97
PERFORMANCE-MONITORING EVENTS
D2H 01H RAT_STALLS.
ROB_READ_PORT
ROB read port
stalls cycles
This event counts the number of cycles
when ROB read port stalls occurred, which
did not allow new micro-ops to enter the
out-of-order pipeline.
Note that, at this stage in the pipeline,
additional stalls may occur at the same
cycle and prevent the stalled micro-ops
from entering the pipe. In such a case,
micro-ops retry entering the execution
pipe in the next cycle and the ROB-read-
port stall is counted again.
D2H 02H RAT_STALLS.
PARTIAL_CYCLES
Partial register
stall cycles
This event counts the number of cycles
instruction execution latency became
longer than the defined latency because
the instruction uses a register that was
partially written by previous instructions.
D2H 04H RAT_STALLS.
FLAGS
Flag stall cycles This event counts the number of cycles
during which execution stalled due to
several reasons, one of which is a partial
flag register stall.
A partial register stall may occur when
two conditions are met:
an instruction modifies some, but not
all, of the flags in the flag register
the next instruction, which depends on
flags, depends on flags that were not
modified by this instruction
D2H 08H RAT_STALLS.
FPSW
FPU status
word stall
This event indicates that the FPU status
word (FPSW) is written. To obtain the
number of times the FPSW is written
divide the event count by 2.
The FPSW is written by instructions with
long latency; a small count may indicate a
high penalty.
D2H 0FH RAT_STALLS.
ANY
All RAT stall
cycles
This event counts the number of stall
cycles due to conditions described by:
RAT_STALLS.ROB_READ_PORT
•RAT_STALLS.PARTIAL
•RAT_STALLS.FLAGS
•RAT_STALLS.FPSW.
Table A-6. Non-Architectural Performance Events
in Processors Based on Intel Core Microarchitecture (Contd.)
Event
Num
Umask
Value Event Name Definition
Description and
Comment