--- a/docs/man3/libpfm_intel_x86_arch.3
+++ b/docs/man3/libpfm_intel_x86_arch.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_x86_arch - support for Intel X86 architectural PMU
 .SH SYNOPSIS
@@ -19,12 +19,10 @@
 The following modifiers are supported on Intel architectural PMU:
 .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
@@ -42,6 +40,17 @@
 Measure on both threads at the same time assuming hyper-threading is enabled. This modifier requires
 at least version 3 of the architectural PMU. This is a boolean modifier.
 
+.SH ENVIRONMENT VARIABLES
+It is possible to force activation of the Intel X86 architectural PMU support using the \fBLIBPFM_FORCE_PMU\fR variable.
+The PMU name, ix8arch, must be passed. The following additional options may be passed using the syntax below:
+.ce
+.B LIBPFM_FORCE_PMU=ix86arch,version
+
+Where the components of the string are defined as follows:
+.TP
+.B version
+The desired architectural PMU revision number, which starts at 1. If the number is not supported, the highest know
+version will be used.
 .SH AUTHORS
 .nf
 Stephane Eranian <eranian@gmail.com>