more comments, slightly safer IEC

c64/kernal/vector.s

@@ -1,4 +1,12 @@
-; Functions defined on pp272-273 of C64 Programmers Reference Guide
+
+;;
+;; Official Kernal routine, described in:
+;;
+;; - [RG64] C64 Programmer's Reference Guide   - page 293 (RESTOR), 304 (VECTOR)
+;; - [CM64] Compute's Mapping the Commodore 64 - page 237
+;;
+;; CPU registers that has to be preserved (see [RG64]): none
+;;
 
 restor: