added Kernal revision byte

c64/kernal/ff80.interop

@@ -0,0 +1 @@
+Byte telling Kernal version; we can probably put just about anything here, but we want to be distinct from everyone else!

c64/kernal/ff80.kernal_revision.s

@@ -0,0 +1,31 @@
+
+;;
+;; This byte identifies Kernal revision. Sources:
+;; - [CM64]  Compute's Mapping the Commodore 64 (page 242/243)
+;; - [MM]    Marko Mäkelä article, http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c64/revisions.txt
+;; - [VICE]  Checked with ROMs included in VICE emulator
+;;
+;; IDEA: put here a value, that is different from any version currently known, as
+;; a warning that this is not a Commodore Kernal. Currently known numbers for C64 are:
+;;
+;; - $00 - [CM64] then current number    [MM] 901227-02             [VICE] C64 Revision 2
+;; - $03 - [CM64] (not mentionned)       [MM] 901227-02, 901227-03  [VICE] C64 Revision 3
+;; - $43 - [CM64] (not mentionned)       [MM] 251104-04             [VICE] SX-64
+;; - $64 - [CM64] PET64 ROM              [MM] (not mentionned)      [VICE] PET64
+;; - $AA - [CM64] first version of ROM   [MM] 901227-01             [VICE] C64 Revision 1
+;;
+;; Values from unofficial ROMs:
+;; - $03 - SuperCPU ROM 1.40, 2.04, also unofficial 0.7 ROM from [VICE]
+;; 
+;; Values from other Commodore machines:
+;; C128:
+;; - $01 - see https://www.pagetable.com/?p=1058
+;; - $02 - unreleased updated ROM, see https://www.pagetable.com/?p=1058
+;;
+;; XXX check more unofficial C64 ROMs (JiffyDOS, DolphinDOS, etc.) and other machines
+;;     VIC-20, PET, CBM II, 264 series, C65 prototypes, other sources for C128 ROMs
+;;
+
+
+kernal_revision:
+    .byte $FF