//#define M68K_CYCLE_IN_USEC (RISC_CYCLE_IN_USEC * 2)
//#define HORIZ_PERIOD_IN_USEC 63.5555
//#define M6502_CYCLE_IN_USEC 0.9765625
-#define M6808_CYCLE_IN_USEC 0.9765625
-#define M6809_CYCLE_IN_USEC 1.0
+
+//#define MASTER_CLOCK (12000000)
+//#define SOUND_CLOCK (3579000)
+// MDRV_CPU_ADD("maincpu", M6809, MASTER_CLOCK/3/4)
+// MDRV_CPU_PROGRAM_MAP(defender_map)
+// MDRV_CPU_ADD("soundcpu", M6808, SOUND_CLOCK)
+// MDRV_CPU_PROGRAM_MAP(defender_sound_map)
+
+#define M6808_CLOCK_SPEED_IN_HZ (3579000.0 / 4.0)
+#define M6809_CLOCK_SPEED_IN_HZ (1000000.0)
+
+// Actually, it's 1.1176306230790722 usec
+//#define M6808_CYCLE_IN_USEC (0.9765625)
+#define M6808_CYCLE_IN_USEC (1000000.0 / M6808_CLOCK_SPEEK_IN_HZ)
+#define M6809_CYCLE_IN_USEC (1000000.0 / M6809_CLOCK_SPEED_IN_HZ)
//#define USEC_TO_RISC_CYCLES(u) (uint32)(((u) / RISC_CYCLE_IN_USEC) + 0.5)
//#define USEC_TO_M68K_CYCLES(u) (uint32)(((u) / M68K_CYCLE_IN_USEC) + 0.5)