diff --git a/A2Mac/6502.c b/A2Mac/6502.c
index cc3169f..2e469e8 100644
--- a/A2Mac/6502.c
+++ b/A2Mac/6502.c
@@ -330,9 +330,9 @@ static inline void m6502_run() {
 //    unsigned long long s = rdtsc();
     unsigned long long e = (unsigned long long)-1LL;
 
-    for ( unsigned long long int i = 0; i < iterations ; i++ ) {
+//    for ( unsigned long long int i = 0; i < iterations ; i++ ) {
 //    for ( ; m6502.pc ; ) {
-//    for ( ; ; ) {
+    for ( ; ; ) {
         if ( m6502.interrupt_flag ) {
             switch (m6502.interrupt) {
                 case NMI:
diff --git a/A2Mac/Apple2_mmio.h b/A2Mac/Apple2_mmio.h
index 62cabb4..862a015 100644
--- a/A2Mac/Apple2_mmio.h
+++ b/A2Mac/Apple2_mmio.h
@@ -204,45 +204,6 @@ static inline uint16_t fetch16() {
     return word;
 }
 
-/**
- get a 16 bit address from the zp:zp+1
- **/
-static inline uint16_t addr_zp_ind( uint8_t addr ) {
-    return memread16(addr);
-}
-
-/**
- X,ind        ....    X-indexed, indirect         OPC ($LL,X)
- operand is zeropage address;
- effective address is word in (LL + X, LL + X + 1), inc. without carry: C.w($00LL + X)
- **/
-static inline uint16_t addr_X_ind() {
-    return addr_zp_ind( fetch() + m6502.X );
-}
-static inline uint8_t src_X_ind() {
-    return memread( addr_X_ind() );
-}
-static inline uint8_t * dest_X_ind() {
-    return & RAM[ addr_X_ind() ];
-}
-
-/**
- ind,Y        ....    indirect, Y-indexed         OPC ($LL),Y
- operand is zeropage address;
- effective address is word in (LL, LL + 1) incremented by Y with carry: C.w($00LL) + Y
- **/
-static inline uint16_t addr_ind_Y() {
-//    uint8_t a = fetch();
-//    dbgPrintf("addr_ind_Y: %04X + %02X = %04X ", addr_zpg_ind( a ), m6502.Y, addr_zpg_ind( a ) + m6502.Y);
-    return addr_zp_ind( fetch() ) + m6502.Y;
-}
-static inline uint8_t src_ind_Y() {
-    return memread( addr_ind_Y() );
-}
-static inline uint8_t * dest_ind_Y() {
-    return & RAM[ addr_ind_Y() ];
-}
-
 /**
  abs        ....    absolute         OPC $LLHH,X
  operand is address; effective address is address incremented by X with carry **
@@ -306,7 +267,7 @@ static inline uint16_t imm() {
  zpg        ....    zeropage         OPC $LL
  operand is zeropage address (hi-byte is zero, address = $00LL)
  **/
-static inline uint16_t addr_zp() {
+static inline uint8_t addr_zp() {
     return fetch();
 }
 static inline uint8_t src_zp() {
@@ -316,12 +277,51 @@ static inline uint8_t * dest_zp() {
     return & RAM[ addr_zp() ];
 }
 
+/**
+ get a 16 bit address from the zp:zp+1
+ **/
+static inline uint16_t addr_zp_ind( uint8_t addr ) {
+    return memread16(addr);
+}
+
+/**
+ X,ind        ....    X-indexed, indirect         OPC ($LL,X)
+ operand is zeropage address;
+ effective address is word in (LL + X, LL + X + 1), inc. without carry: C.w($00LL + X)
+ **/
+static inline uint16_t addr_X_ind() {
+    return addr_zp_ind( addr_zp() + m6502.X );
+}
+static inline uint8_t src_X_ind() {
+    return memread( addr_X_ind() );
+}
+static inline uint8_t * dest_X_ind() {
+    return & RAM[ addr_X_ind() ];
+}
+
+/**
+ ind,Y        ....    indirect, Y-indexed         OPC ($LL),Y
+ operand is zeropage address;
+ effective address is word in (LL, LL + 1) incremented by Y with carry: C.w($00LL) + Y
+ **/
+static inline uint16_t addr_ind_Y() {
+    //    uint8_t a = fetch();
+    //    dbgPrintf("addr_ind_Y: %04X + %02X = %04X ", addr_zpg_ind( a ), m6502.Y, addr_zpg_ind( a ) + m6502.Y);
+    return addr_zp_ind( addr_zp() ) + m6502.Y;
+}
+static inline uint8_t src_ind_Y() {
+    return memread( addr_ind_Y() );
+}
+static inline uint8_t * dest_ind_Y() {
+    return & RAM[ addr_ind_Y() ];
+}
+
 /**
  zpg,X        ....    zeropage, X-indexed         OPC $LL,X
  operand is zeropage address;
  effective address is address incremented by X without carry **
  **/
-static inline uint16_t addr_zp_X() {
+static inline uint8_t addr_zp_X() {
     return addr_zp() + m6502.X;
 }
 static inline uint8_t src_zp_X() {
@@ -336,7 +336,7 @@ static inline uint8_t * dest_zp_X() {
  operand is zeropage address;
  effective address is address incremented by Y without carry **
  **/
-static inline uint16_t addr_zp_Y() {
+static inline uint8_t addr_zp_Y() {
     return addr_zp() + m6502.Y;
 }
 static inline uint8_t src_zp_Y() {
diff --git a/A2Mac/ViewController.swift b/A2Mac/ViewController.swift
index 61dbb3b..74032ac 100644
--- a/A2Mac/ViewController.swift
+++ b/A2Mac/ViewController.swift
@@ -31,9 +31,19 @@ class ViewController: NSViewController {
         0x228, 0x2A8, 0x328, 0x3A8, 0x050, 0x0D0, 0x150, 0x1D0, 0x250, 0x2D0, 0x350, 0x3D0
     ]
     
+    var workItem : DispatchWorkItem? = nil;
     @IBAction func Power(_ sender: Any) {
-        DispatchQueue.global(qos: .userInitiated).async {
-            tst6502()
+        if ( workItem != nil ) {
+            workItem!.cancel();
+            workItem = nil;
+        }
+        else {
+            workItem = DispatchWorkItem {
+                DispatchQueue.global(qos: .userInitiated).async {
+                    tst6502()
+                }
+            }
+            DispatchQueue.global().async(execute: workItem!);
         }
     }
     
diff --git a/A2Mac/common.h b/A2Mac/common.h
index ad887cb..436de28 100644
--- a/A2Mac/common.h
+++ b/A2Mac/common.h
@@ -41,37 +41,42 @@ union {
 
 #define BITTEST(n,x) ((bits_t)(n)).b##x
 
-static inline void set_flags_N( uint8_t test ) {
+static inline void set_flags_N( const uint8_t test ) {
     m6502.flags.N = BITTEST(test, 7);
     dbgPrintf("%c", m6502.flags.N ? 'N' : 'n');
 }
 
-static inline void set_flags_V( uint8_t test ) {
+static inline void set_flags_V( const uint8_t test ) {
     m6502.flags.V = BITTEST(test, 6);
     dbgPrintf("%c", m6502.flags.V ? 'V' : 'v');
 }
 
-static inline void set_flags_Z( uint8_t test ) {
+static inline void set_flags_Z( const uint8_t test ) {
     m6502.flags.Z = test == 0;
     dbgPrintf("%c", m6502.flags.Z ? 'Z' : 'z');
 }
 
-static inline void set_flags_C( int test ) {
+static inline void set_flags_C( const int test ) {
     m6502.flags.C = test >= 0;
     dbgPrintf("%c", m6502.flags.C ? 'C' : 'c');
 }
 
-static inline void set_flags_NZ( uint8_t test ) {
+static inline void set_flags_NZ( const uint8_t test ) {
     set_flags_N(test);
     set_flags_Z(test);
 }
 
-static inline void set_flags_NVZ( uint8_t test ) {
+static inline void set_flags_NV( const uint8_t test ) {
+    set_flags_N(test);
+    set_flags_V(test);
+}
+
+static inline void set_flags_NVZ( const uint8_t test ) {
     set_flags_NZ(test);
     set_flags_V(test);
 }
 
-static inline void set_flags_NZC( int test ) {
+static inline void set_flags_NZC( const int test ) {
     set_flags_NZ(test);
     set_flags_C(test);
 }
diff --git a/A2Mac/instructions/6502_instr_arithmetic.h b/A2Mac/instructions/6502_instr_arithmetic.h
index 5a9af8b..425edcf 100644
--- a/A2Mac/instructions/6502_instr_arithmetic.h
+++ b/A2Mac/instructions/6502_instr_arithmetic.h
@@ -31,8 +31,7 @@
 **/
 static inline void ADC( uint8_t imm ) {
     dbgPrintf("ADC(%02X) A:%02X + %02X ", imm, m6502.A, imm);
-    m6502.A += imm + m6502.flags.C;
-    set_flags_NZCV( m6502.A );
+    set_flags_NZCV( m6502.A += imm + m6502.flags.C );
     dbgPrintf("-> A:%02X ", m6502.A);
 }
 
diff --git a/A2Mac/instructions/6502_instr_compare_test.h b/A2Mac/instructions/6502_instr_compare_test.h
index 1a8b214..ff6fb05 100644
--- a/A2Mac/instructions/6502_instr_compare_test.h
+++ b/A2Mac/instructions/6502_instr_compare_test.h
@@ -26,9 +26,8 @@
  **/
 static inline void BIT( uint8_t imm ) {
     dbgPrintf("BIT(%02X) ", imm);
-    m6502.flags.N = BITTEST(imm, 7);
-    m6502.flags.V = BITTEST(imm, 6);
-    m6502.flags.Z = (imm & m6502.A) == 0;
+    set_flags_NV(imm);
+    set_flags_Z(m6502.A & imm);
 }
 
 /**
diff --git a/A2Mac/instructions/6502_instr_logic.h b/A2Mac/instructions/6502_instr_logic.h
index 0dc5f70..544608e 100644
--- a/A2Mac/instructions/6502_instr_logic.h
+++ b/A2Mac/instructions/6502_instr_logic.h
@@ -29,8 +29,7 @@
 **/
 static inline void ORA( uint8_t imm ) {
     dbgPrintf("ORA(%02X) ", imm);
-    m6502.A |= imm;
-    set_flags_NZ( m6502.A );
+    set_flags_NZ( m6502.A |= imm );
 }
 
 /**
@@ -52,8 +51,7 @@ static inline void ORA( uint8_t imm ) {
  **/
 static inline void AND( uint8_t imm ) {
     dbgPrintf("AND(%02X) ", imm);
-    m6502.A &= imm;
-    set_flags_NZ( m6502.A );
+    set_flags_NZ( m6502.A &= imm );
 }
 
 /**
@@ -75,8 +73,7 @@ static inline void AND( uint8_t imm ) {
 **/
 static inline void EOR( uint8_t imm ) {
     dbgPrintf("EOR(%02X) ", imm);
-    m6502.A ^= imm;
-    set_flags_NZ( m6502.A );
+    set_flags_NZ( m6502.A ^= imm );
 }
 
 #endif // __6502_INSTR_LOGIC_H__
diff --git a/A2Mac/instructions/6502_instr_shift_rotate.h b/A2Mac/instructions/6502_instr_shift_rotate.h
index 2f07598..50fdd86 100644
--- a/A2Mac/instructions/6502_instr_shift_rotate.h
+++ b/A2Mac/instructions/6502_instr_shift_rotate.h
@@ -54,13 +54,11 @@ static inline void ASLA() {
 static inline void LSR( uint8_t * dst ) {
     dbgPrintf("LSR ");
     m6502.flags.C = *dst & 1;
-    ;
     set_flags_NZ( *dst >>= 1 );
 }
 static inline void LSRA() {
     dbgPrintf("LSR ");
     m6502.flags.C = m6502.A & 1;
-    ;
     set_flags_NZ( m6502.A >>= 1 );
 }
 
@@ -83,7 +81,6 @@ static inline void ROL( uint8_t * dst ) {
     uint8_t C = m6502.flags.C;
     m6502.flags.C = *dst >> 7;
     *dst <<= 1;
-    ;
     set_flags_NZ( *dst |= C );
 }
 static inline void ROLA() {
@@ -91,7 +88,6 @@ static inline void ROLA() {
     uint8_t C = m6502.flags.C;
     m6502.flags.C = m6502.A >> 7;
     m6502.A <<= 1;
-    ;
     set_flags_NZ( m6502.A |= C );
 }
 
@@ -114,7 +110,6 @@ static inline void ROR( uint8_t * dst ) {
     uint8_t C = m6502.flags.C << 7;
     m6502.flags.C = *dst & 1;
     *dst >>= 1;
-    ;
     set_flags_NZ( *dst |= C );
 }
 static inline void RORA() {
@@ -122,7 +117,6 @@ static inline void RORA() {
     uint8_t C = m6502.flags.C << 7;
     m6502.flags.C = m6502.A & 1;
     m6502.A >>= 1;
-    ;
     set_flags_NZ( m6502.A |= C );
 }
 
diff --git a/A2Mac/instructions/6502_instr_stack.h b/A2Mac/instructions/6502_instr_stack.h
index f5efa01..266212d 100644
--- a/A2Mac/instructions/6502_instr_stack.h
+++ b/A2Mac/instructions/6502_instr_stack.h
@@ -9,22 +9,24 @@
 #ifndef __6502_INSTR_STACK_H__
 #define __6502_INSTR_STACK_H__
 
+static const uint16_t stack_base_addr = 0x100;
 
-static inline void PUSH( uint8_t n ) {
-    RAM[ 0x100 + m6502.sp-- ] = n;
+
+static inline void PUSH( uint8_t imm ) {
+    RAM[ stack_base_addr + m6502.sp-- ] = imm;
 }
 
 static inline uint8_t POP() {
-    return RAM[ 0x100 + (++m6502.sp) ];
+    return RAM[ ++m6502.sp + stack_base_addr ];
 }
 
 static inline void PUSH_addr( uint16_t addr ) {
-    PUSH( (uint8_t)addr );
     PUSH( (uint8_t)(addr >> 8) );
+    PUSH( (uint8_t)addr );
 }
 
 static inline uint16_t POP_addr() {
-    return ( POP() << 8 ) + POP();
+    return  POP() + ( POP() << 8 );
 }
 
 
diff --git a/A2Mac/instructions/6502_instr_transfer.h b/A2Mac/instructions/6502_instr_transfer.h
index e2a750c..93a538c 100644
--- a/A2Mac/instructions/6502_instr_transfer.h
+++ b/A2Mac/instructions/6502_instr_transfer.h
@@ -22,8 +22,7 @@
  **/
 static inline void TAX() {
     dbgPrintf("TAX ");
-    m6502.X = m6502.A;
-    set_flags_NZ(m6502.X);
+    set_flags_NZ(m6502.X = m6502.A);
 }
 
 /**
@@ -38,8 +37,7 @@ static inline void TAX() {
  **/
 static inline void TXA() {
     dbgPrintf("TXA ");
-    m6502.A = m6502.X;
-    set_flags_NZ(m6502.A);
+    set_flags_NZ(m6502.A = m6502.X);
 }
 
 
@@ -55,8 +53,7 @@ static inline void TXA() {
  **/
 static inline void TAY() {
     dbgPrintf("TAY ");
-    m6502.Y = m6502.A;
-    set_flags_NZ(m6502.Y);
+    set_flags_NZ(m6502.Y = m6502.A);
 }
 
 /**
@@ -71,8 +68,7 @@ static inline void TAY() {
  **/
 static inline void TYA() {
     dbgPrintf("TYA ");
-    m6502.A = m6502.Y;
-    set_flags_NZ(m6502.A);
+    set_flags_NZ(m6502.A = m6502.Y);
 }
 
 /**
@@ -87,8 +83,7 @@ static inline void TYA() {
  **/
 static inline void TSX() {
     dbgPrintf("TSX ");
-    m6502.X = m6502.sp;
-    set_flags_NZ(m6502.X);
+    set_flags_NZ(m6502.X = m6502.sp);
 }
 
 /**