--- a/docs/man3/libpfm_intel_p6.3
+++ b/docs/man3/libpfm_intel_p6.3
@@ -1,4 +1,4 @@
-.TH LIBPFM 3  "September, 2009" "" "Linux Programmer's Manual"
+.TH LIBPFM 4  "September, 2009" "" "Linux Programmer's Manual"
 .SH NAME
  libpfm_intel_p6 - support for Intel P5 based processors
 .SH SYNOPSIS
@@ -16,12 +16,10 @@
 The following modifiers are supported on all Intel P6 processors:
 .TP
 .B u
-Measure at user level which includes privilege levels 1, 2, 3. This corresponds to \fBPFM_PLM3\fR.
-This is a boolean modifier.
+Measure at user level which includes privilege levels 1, 2, 3. This is a boolean modifier.
 .TP
 .B k
-Measure at kernel level which includes privilege level 0. This corresponds to \fBPFM_PLM0\fR.
-This is a boolean modifier.
+Measure at kernel level which includes privilege level 0. This is a boolean modifier.
 .TP
 .B i
 Invert the meaning of the event. The counter will now count cycles in which the event is \fBnot\fR
@@ -34,6 +32,10 @@
 Set the counter mask value. The mask acts as a threshold. The counter will count the number of cycles
 in which the number of occurrences of the event is greater or equal to the threshold. This is an integer
 modifier with values in the range [0:255].
+
+.SH ENVIRONMENT VARIABLES
+It is possible to force activation of a specific Intel P6 processors using the \fBLIBPFM_FORCE_PMU\fR variable.
+One of the PMU names listed in the synopsis must be specified.
 .SH AUTHORS
 .nf
 Stephane Eranian <eranian@gmail.com>