From 51f8b2b340baf7f92e23e998335bd7cede3fd313 Mon Sep 17 00:00:00 2001
From: Marco Maccaferri <marco.maccaferri@maccasoft.com>
Date: Wed, 1 May 2019 09:53:37 +0200
Subject: [PATCH] More accurate emulator timing

---
 src/com/maccasoft/tools/Machine.java | 15 ++++++++-------
 src/z80core/MemIoOps.java            |  3 ++-
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/com/maccasoft/tools/Machine.java b/src/com/maccasoft/tools/Machine.java
index 20c90e9..30ff364 100644
--- a/src/com/maccasoft/tools/Machine.java
+++ b/src/com/maccasoft/tools/Machine.java
@@ -55,7 +55,6 @@ public class Machine extends MemIoOps {
     Z80 proc;
     Thread thread;
     double clockNs;
-    long tstates;
 
     public Machine() {
         rom = new byte[16384];
@@ -108,16 +107,18 @@ public class Machine extends MemIoOps {
 
         while (!Thread.interrupted()) {
             synchronized (proc) {
-                long current = System.nanoTime();
-                long tstates = getTstates() + (long) ((current - ns) / clockNs);
-                while (getTstates() < tstates) {
-                    proc.execute();
+                int runTstates = (int) ((System.nanoTime() - ns) / clockNs);
+                if (runTstates >= 4) {
+                    long prevTstates = tstates;
+                    while (tstates < (prevTstates + runTstates)) {
+                        proc.execute();
+                    }
+                    ns += (tstates - prevTstates) * clockNs;
                 }
-                ns = current;
             }
 
             try {
-                Thread.sleep(1);
+                Thread.sleep(1L);
             } catch (InterruptedException e) {
                 break;
             }
diff --git a/src/z80core/MemIoOps.java b/src/z80core/MemIoOps.java
index 6697536..3caa434 100644
--- a/src/z80core/MemIoOps.java
+++ b/src/z80core/MemIoOps.java
@@ -13,7 +13,8 @@ public class MemIoOps {
 
     private byte[] z80Ram;
     private byte[] z80Ports;
-    private long tstates = 0;
+
+    protected long tstates = 0;
 
     public MemIoOps() {