#define REG_P_REST r8
#define REG_NZ r9 // 14
#define REG_ADDR r10 // 18
-#define REG_CYCLE r11 // 1c
+#define REG_CYCLE r11 // 1c [31:16] - fceu cycles, [15:8] - fceu irqhook cycles, [7:0] - fceu timestamp cycles
#define REG_OP_TABLE r12 // 20
* note: fceu uses this differently
* [7:0] - interrupt flags (same as above)
* [15:8] - FCEU IRQ pending sources
- * [23:16] - unused
+ * [16] - a flag which indicates that MapIRQHook is not null
+ * [23:17] - unused
* [31:24] - stack pointer
*/