Make "Pop" more like "Read". i.e. don't return a result, just use the value placed on the "bus"

EightBit/BigEndianProcessor.cs

@@ -51,8 +51,10 @@ namespace EightBit
         protected override void PopInto(Register16 into)
         {
             //ArgumentNullException.ThrowIfNull(into);
-            into.High = this.Pop();
-            into.Low = this.Pop();
+            this.Pop();
+            into.High = this.Bus.Data;
+            this.Pop();
+            into.Low = this.Bus.Data;
         }
 
         protected override void PushShort(Register16 value)

EightBit/IntelProcessor.cs

@@ -148,11 +148,10 @@ namespace EightBit
             this.MemoryWrite(this.SP, value);
         }
 
-        protected sealed override byte Pop()
+        protected sealed override void Pop()
         {
             this.MemoryRead(this.SP);
             this.SP.Increment();
-            return this.Bus.Data;
         }
 
         protected sealed override void GetShort()

EightBit/LittleEndianProcessor.cs

@@ -52,8 +52,10 @@ namespace EightBit
         protected override void PopInto(Register16 into)
         {
             //ArgumentNullException.ThrowIfNull(into);
-            into.Low = this.Pop();
-            into.High = this.Pop();
+            this.Pop();
+            into.Low = this.Bus.Data;
+            this.Pop();
+            into.High = this.Bus.Data;
         }
 
         protected override void PushShort(Register16 value)

EightBit/Processor.cs

@@ -267,7 +267,7 @@ namespace EightBit
 
         protected abstract void Push(byte value);
 
-        protected abstract byte Pop();
+        protected abstract void Pop();
 
         protected abstract void PushShort(Register16 value);
 

LR35902/LR35902.FuseTest/TestRunner.cs

@@ -22,12 +22,14 @@ namespace LR35902.FuseTest
         private readonly Test<T> test = test;
         private readonly Result<T> result = result;
         private readonly EightBit.Ram ram = new(0x10000);
+        private EightBit.MemoryMapping? mapping;
 
         public bool Failed { get; private set; } = false;
 
         public bool Unimplemented { get; private set; } = false;
 
-        public override EightBit.MemoryMapping Mapping(ushort address) => new(this.ram, 0, EightBit.Mask.Sixteen, EightBit.AccessLevel.ReadWrite);
+        public override EightBit.MemoryMapping Mapping(ushort address) =>
+            this.mapping ??= new EightBit.MemoryMapping(this.ram, 0, EightBit.Mask.Sixteen, EightBit.AccessLevel.ReadWrite);
 
         public void Run()
         {

M6502/Core.cs

@@ -586,11 +586,10 @@ namespace M6502
 
         #region Stack access
 
-        protected override byte Pop()
+        protected override void Pop()
         {
             this.RaiseStack();
             this.MemoryRead();
-            return this.Bus.Data;
         }
 
         protected override void Push(byte value)
@@ -861,7 +860,7 @@ namespace M6502
 
         private void STX() => this.MemoryWrite(this.X);
 
-        private void LDY() => this.Y = this.Through();
+        protected void LDY() => this.Y = this.Through();
 
         private void STY() => this.MemoryWrite(this.Y);
 
@@ -1105,7 +1104,8 @@ namespace M6502
         private void PLA()
         {
             this.SwallowPop();
-            this.A = this.Through(this.Pop());
+            this.Pop();
+            this.LDA();
         }
 
         private void PHP() => this.Push(SetBit(this.P, StatusBits.BF));
@@ -1113,7 +1113,8 @@ namespace M6502
         private void PLP()
         {
             this.SwallowPop();
-            this.P = ClearBit(SetBit(this.Pop(), StatusBits.RF), StatusBits.BF);
+            this.Pop();
+            this.P = ClearBit(SetBit(this.Bus.Data, StatusBits.RF), StatusBits.BF);
         }
 
         private void RTI()

M6502/M6502.HarteTest/TestRunner.cs

@@ -6,8 +6,8 @@
     {
         public Ram RAM { get; } = new(0x10000);
 
-        public MOS6502 CPU { get; }
-        //public WDC65C02 CPU { get; }
+        //public MOS6502 CPU { get; }
+        public WDC65C02 CPU { get; }
 
         private readonly MemoryMapping _mapping;
 

M6502/WDC65C02.cs

@@ -353,7 +353,8 @@ namespace M6502
         private void PLX()
         {
             this.SwallowPop();
-            this.X = this.Through(this.Pop());
+            this.Pop();
+            this.LDX();
         }
 
         private void PHY() => this.Push(this.Y);
@@ -361,7 +362,8 @@ namespace M6502
         private void PLY()
         {
             this.SwallowPop();
-            this.Y = this.Through(this.Pop());
+            this.Pop();
+            this.LDY();
         }
 
         private void BRA() => this.Branch(true);

MC6809/MC6809.cs

@@ -593,7 +593,7 @@ namespace MC6809
 
         #region Push/Pop
 
-        protected override byte Pop() => this.PopS();
+        protected override void Pop() => this.PopS();
 
         protected override void Push(byte value) => this.PushS(value);
 
@@ -611,19 +611,20 @@ namespace MC6809
             this.Push(stack, value.High);
         }
 
-        protected byte Pop(Register16 stack)
+        protected void Pop(Register16 stack)
         {
             this.MemoryRead(stack);
             stack.Increment();
-            return this.Bus.Data;
         }
 
-        private byte PopS() => this.Pop(this.S);
+        private void PopS() => this.Pop(this.S);
 
         protected Register16 PopWord(Register16 stack)
         {
-            this.Intermediate.High = this.Pop(stack);
-            this.Intermediate.Low = this.Pop(stack);
+            this.Pop(stack);
+            this.Intermediate.High = this.Bus.Data;
+            this.Pop(stack);
+            this.Intermediate.Low = this.Bus.Data;
             return this.Intermediate;
         }
 
@@ -1054,22 +1055,26 @@ namespace MC6809
 
             if ((control & (byte)Bits.Bit0) != 0)
             {
-                this.CC = this.Pop(stack);
+                this.Pop(stack);
+                this.CC = this.Bus.Data;
             }
 
             if ((control & (byte)Bits.Bit1) != 0)
             {
-                this.A = this.Pop(stack);
+                this.Pop(stack);
+                this.A = this.Bus.Data;
             }
 
             if ((control & (byte)Bits.Bit2) != 0)
             {
-                this.B = this.Pop(stack);
+                this.Pop(stack);
+                this.B = this.Bus.Data;
             }
 
             if ((control & (byte)Bits.Bit3) != 0)
             {
-                this.DP = this.Pop(stack);
+                this.Pop(stack);
+                this.DP = this.Bus.Data;
             }
 
             // Sixteen-bit registers