diff --git a/docs/index.rst b/docs/index.rst
index 70b350a..61244c9 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -165,8 +165,7 @@ Command Reference
 
 .. describe:: disassemble <address_range>
 
-  Disassembles a range of memory.  All legal NMOS 6502 opcodes and addressing
-  modes are supported::
+  Disassemble a range of memory::
 
     .disassemble ff80:ff84
     $ff80  d8        CLD
@@ -174,6 +173,11 @@ Command Reference
     $ff83  9a        TXS
     $ff84  a0 1c     LDY #$1c
 
+  The disassembly will use the instruction set of the selected MPU.  For
+  example, the extra instructions of the 65C02 will only be displayed if
+  a 65C02 MPU is selected.  On an NMOS 6502, those instructions would be
+  disassembled as ``???``.
+
   If labels have been defined, they will be substituted for
   addresses in the operands.