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

Table Of Contents
Vol. 3 A-155
PERFORMANCE-MONITORING EVENTS
ESCR restrictions MSR_FIRM_ESCR0
MSR_FIRM_ESCR1
Counter numbers
per ESCR
ESCR0: 8, 9
ESCR1: 10, 11
ESCR Event Select 34H ESCR[31:25]
ESCR Event Mask
15: ALL
ESCR[24:9]
Count assists for SSE/SSE2/SSE3
μops.
CCCR Select 01H CCCR[15:13]
Event Specific
Notes
1: Not all requests for assists are
actually taken. This event is
known to overcount in that it
counts requests for assists
from instructions on the non-
retired path that do not incur a
performance penalty. An assist
is actually taken only for non-
bogus μops. Any appreciable
counts for this event are an
indication that the DAZ or FTZ
bit should be set and/or the
source code should be changed
to eliminate the condition.
2: Two common situations for an
SSE/SSE2/SSE3 operation
needing an assist are: (1) when
a denormal constant is used as
an input and the Denormals-
Are-Zero (DAZ) mode is not
set, (2) when the input operand
uses the underflowed result of
a previous SSE/SSE2/SSE3
operation and neither the DAZ
nor Flush-To-Zero (FTZ) modes
are set.
Table A-9. Performance Monitoring Events Supported by Intel NetBurst
Microarchitecture for Non-Retirement Counting (Contd.)
Event Name Event Parameters Parameter Value Description