for MEGA65 disabled FAST/SLOW commands in native mode

src/basic/basic_commands_01/cmd_fast_slow.s

@@ -5,6 +5,32 @@
 
 !ifdef CONFIG_MB_M65 {
 
+; NOTE: In native mode the system should not run at 1 MHz speed - it's dangerous,
+;       as it uses compound instructions, which are not safe in 1MHz mode
+
+cmd_slow: ; set CPU speed to 1 MHz
+
+	jsr helper_ensure_legacy_mode
+
+	lda #$40
+	bra cmd_slow_fast_common
+
+	; FALLTROUGH
+
+cmd_fast: ; set CPU speed to 40 MHz
+
+	jsr helper_ensure_legacy_mode
+
+	lda #$41
+
+	; FALLTROUGH
+
+cmd_slow_fast_common:
+
+	sta CPU_D6510
+	rts
+
+
 	; For MEGA65 Kernal routines are called directly
 
 } else ifdef CONFIG_MB_U64 {