diff --git a/htop.1.in b/htop.1.in
index afd882e4..b2eba5d1 100644
--- a/htop.1.in
+++ b/htop.1.in
@@ -376,6 +376,15 @@ The user ID of the process owner.
 .TP
 .B PERCENT_CPU (CPU%)
 The percentage of the CPU time that the process is currently using.
+This is the default way to represent CPU usage in Linux. Each process can
+consume up to 100% which means the full capacity of the core it is running
+on. This is sometimes called "Irix mode" e.g. in
+.BR top (1).
+.TP
+.B PERCENT_NORM_CPU (NCPU%)
+The percentage of the CPU time that the process is currently using normalized
+by CPU count. This is sometimes called "Solaris mode" e.g. in
+.BR top (1).
 .TP
 .B PERCENT_MEM (MEM%)
 The percentage of memory the process is currently using (based on the process's