From a9e5913d0c02cc1c7555083e3f4079e2204add6b Mon Sep 17 00:00:00 2001
From: Peter Schorn <peter.schorn@acm.org>
Date: Sun, 26 Apr 2015 09:50:00 +0200
Subject: [PATCH] AltairZ80: Reduced polling for CPU stop on non UNIX platforms

---
 AltairZ80/altairz80_cpu.c       | 22 ++++++++++++++++++++--
 AltairZ80/altairz80_cpu_nommu.c |  8 ++++++--
 AltairZ80/i86_decode.c          |  8 ++++++--
 AltairZ80/m68ksim.c             |  8 ++++++--
 4 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/AltairZ80/altairz80_cpu.c b/AltairZ80/altairz80_cpu.c
index 80e69aa0..e51bb1a3 100644
--- a/AltairZ80/altairz80_cpu.c
+++ b/AltairZ80/altairz80_cpu.c
@@ -2047,6 +2047,24 @@ void setClockFrequency(const uint32 Value) {
     clockHasChanged = TRUE;
 }
 
+
+#if !UNIX_PLATFORM
+
+/* Poll for CPU stop when user presses sim_int_char. Must be followed by sim_process_event */
+
+#define INITIAL_POLL_COUNTER    1000
+
+void pollForCPUStop(void) {
+    static uint32 pollCounter = INITIAL_POLL_COUNTER;
+    if (--pollCounter <= 0) {
+        pollCounter = INITIAL_POLL_COUNTER;
+        sim_poll_kbd(); /* the following sim_process_event will check for stop */
+    }
+}
+
+#endif
+
+
 static t_stat sim_instr_mmu (void) {
     extern int32 timerInterrupt;
     extern int32 timerInterruptHandler;
@@ -2099,8 +2117,8 @@ static t_stat sim_instr_mmu (void) {
     while (switch_cpu_now == TRUE) {        /* loop until halted    */
         if (sim_interval <= 0) {            /* check clock queue    */
 #if !UNIX_PLATFORM
-            /* poll on platforms without reliable signalling */
-            sim_poll_kbd(); /* following sim_process_event will check for stop */
+            /* poll on platforms without reliable signalling but not too often */
+            pollForCPUStop(); /* following sim_process_event will check for stop */
 #endif
             if ((reason = sim_process_event()))
                 break;
diff --git a/AltairZ80/altairz80_cpu_nommu.c b/AltairZ80/altairz80_cpu_nommu.c
index b8c68769..d2535a7f 100644
--- a/AltairZ80/altairz80_cpu_nommu.c
+++ b/AltairZ80/altairz80_cpu_nommu.c
@@ -124,6 +124,10 @@ extern int32 IFF_S; /* Interrupt Flip Flop                          */
 extern int32 IR_S;  /* Interrupt (upper) / Refresh (lower) register */
 extern int32 chiptype;
 
+#if !UNIX_PLATFORM
+extern void pollForCPUStop(void);
+#endif
+
 /* the following tables precompute some common subexpressions
     parityTable[i]          0..255  (number of 1's in i is odd) ? 0 : 4
     incTable[i]             0..256! (i & 0xa8) | (((i & 0xff) == 0) << 6) | (((i & 0xf) == 0) << 4)
@@ -1016,8 +1020,8 @@ t_stat sim_instr_nommu(void) {
     while (TRUE) {                                  /* loop until halted    */
         if (sim_interval <= 0) {                    /* check clock queue    */
 #if !UNIX_PLATFORM
-            /* poll on platforms without reliable signalling */
-            sim_poll_kbd(); /* following sim_process_event will check for stop */
+            /* poll on platforms without reliable signalling but not too often */
+            pollForCPUStop(); /* following sim_process_event will check for stop */
 #endif
             if ((reason = sim_process_event()))
                 break;
diff --git a/AltairZ80/i86_decode.c b/AltairZ80/i86_decode.c
index fe25c5e7..7684b613 100644
--- a/AltairZ80/i86_decode.c
+++ b/AltairZ80/i86_decode.c
@@ -44,6 +44,10 @@ extern int32 PCX_S;     /* PC register (8086), 20 bit                   */
 extern uint32 PCX;      /* external view of PC                          */
 extern UNIT cpu_unit;
 
+#if !UNIX_PLATFORM
+extern void pollForCPUStop(void);
+#endif
+
 void i86_intr_raise(PC_ENV *m,uint8 intrnum);
 void cpu8086reset(void);
 t_stat sim_instr_8086(void);
@@ -209,8 +213,8 @@ t_stat sim_instr_8086(void) {
     while (switch_cpu_now == TRUE) {                        /* loop until halted    */
         if (sim_interval <= 0) {                            /* check clock queue    */
 #if !UNIX_PLATFORM
-            /* poll on platforms without reliable signalling */
-            sim_poll_kbd(); /* following sim_process_event will check for stop */
+            /* poll on platforms without reliable signalling but not too often */
+            pollForCPUStop(); /* following sim_process_event will check for stop */
 #endif
             if ( (reason = sim_process_event()) )
                 break;
diff --git a/AltairZ80/m68ksim.c b/AltairZ80/m68ksim.c
index 76f1853c..f25cec54 100644
--- a/AltairZ80/m68ksim.c
+++ b/AltairZ80/m68ksim.c
@@ -158,6 +158,10 @@ static uint32 m68k_fc;                              /* Current function code fro
 extern uint32 m68k_registers[M68K_REG_CPU_TYPE + 1];
 extern UNIT cpu_unit;
 
+#if !UNIX_PLATFORM
+extern void pollForCPUStop(void);
+#endif
+
 #define M68K_BOOT_LENGTH        (32 * 1024)                 /* size of bootstrap    */
 #define M68K_BOOT_PC            0x000400                    /* initial PC for boot  */
 #define M68K_BOOT_SP            0xfe0000                    /* initial SP for boot  */
@@ -215,8 +219,8 @@ t_stat sim_instr_m68k(void) {
     while (TRUE) {
         if (sim_interval <= 0) {                            /* check clock queue    */
 #if !UNIX_PLATFORM
-            /* poll on platforms without reliable signalling */
-            sim_poll_kbd(); /* following sim_process_event will check for stop */
+            /* poll on platforms without reliable signalling but not too often */
+            pollForCPUStop(); /* following sim_process_event will check for stop */
 #endif
             if ((reason = sim_process_event()))
                 break;