diff --git a/BizHawk.Emulation.Cores/CPUs/Z80A/Execute.cs b/BizHawk.Emulation.Cores/CPUs/Z80A/Execute.cs
index 299d84dd0f..4159f31d7a 100644
--- a/BizHawk.Emulation.Cores/CPUs/Z80A/Execute.cs
+++ b/BizHawk.Emulation.Cores/CPUs/Z80A/Execute.cs
@@ -23,7 +23,6 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 		public bool NO_prefix, CB_prefix, IX_prefix, EXTD_prefix, IY_prefix, IXCB_prefix, IYCB_prefix;
 		public bool IXCB_prefetch, IYCB_prefetch; // value is fetched before opcode
 		public bool halted;
-		public bool jammed;
 		public ushort PF;
 
 		public void FetchInstruction(byte opcode)
@@ -617,7 +616,7 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 					case 0x74: INT_OP(NEG, A);							break; // NEG
 					case 0x75: RETN_();									break; // RETN
 					case 0x76: INT_MODE_(1);							break; // IM $1
-					case 0x77: JAM_();									break; // JAM
+					case 0x77: NOP_();									break; // NOP
 					case 0x78: IN_REG_(A, C);							break; // IN A, (C)
 					case 0x79: OUT_REG_(C, A);							break; // OUT (C), A
 					case 0x7A: REG_OP_16_(ADC16, L, H, SPl, SPh);		break; // ADC HL, SP
@@ -625,7 +624,7 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 					case 0x7C: INT_OP(NEG, A);							break; // NEG
 					case 0x7D: RETN_();									break; // RETI
 					case 0x7E: INT_MODE_(2);							break; // IM $2
-					case 0x7F: JAM_();									break; // JAM
+					case 0x7F: NOP_();									break; // NOP
 					case 0xA0: LD_OP_R(INC16, 0);						break; // LDI
 					case 0xA1: CP_OP_R(INC16, 0);						break; // CPI
 					case 0xA2: IN_OP_R(INC16, 0);						break; // INI
@@ -642,7 +641,7 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 					case 0xB9: CP_OP_R(DEC16, 1);						break; // CPDR
 					case 0xBA: IN_OP_R(DEC16, 1);						break; // INDR
 					case 0xBB: OUT_OP_R(DEC16, 1);						break; // OTDR
-					default: JAM_();									break; // JAM
+					default: NOP_();									break; // NOP
 
 				}
 			}
diff --git a/BizHawk.Emulation.Cores/CPUs/Z80A/Tables_Direct.cs b/BizHawk.Emulation.Cores/CPUs/Z80A/Tables_Direct.cs
index ce40eea385..8e473d1527 100644
--- a/BizHawk.Emulation.Cores/CPUs/Z80A/Tables_Direct.cs
+++ b/BizHawk.Emulation.Cores/CPUs/Z80A/Tables_Direct.cs
@@ -448,15 +448,6 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 						OP };
 		}
 
-		private void JAM_()
-		{
-			cur_instr = new ushort[]
-						{JAM,
-						IDLE,
-						IDLE,
-						IDLE };
-		}
-
 		private void OUT_()
 		{
 			cur_instr = new ushort[]
diff --git a/BizHawk.Emulation.Cores/CPUs/Z80A/Z80A.cs b/BizHawk.Emulation.Cores/CPUs/Z80A/Z80A.cs
index 2fb1103373..9155aeb178 100644
--- a/BizHawk.Emulation.Cores/CPUs/Z80A/Z80A.cs
+++ b/BizHawk.Emulation.Cores/CPUs/Z80A/Z80A.cs
@@ -61,20 +61,20 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 		public const ushort PREFETCH = 46;
 		public const ushort ASGN = 47;
 		public const ushort ADDS = 48; // signed 16 bit operation used in 2 instructions
-		public const ushort JAM = 49;  // all undocumented opcodes jam the machine
+		public const ushort INT_MODE = 49;
 		public const ushort EI_RETN = 50;
 		public const ushort EI_RETI = 51; // reti has no delay in interrupt enable
 		public const ushort OUT = 52;
 		public const ushort IN = 53;
 		public const ushort NEG = 54;		
-		public const ushort INT_MODE = 55;	
-		public const ushort RRD = 56;
-		public const ushort RLD = 57;		
-		public const ushort SET_FL_LD = 58;
-		public const ushort SET_FL_CP = 59;
+		public const ushort RRD = 55;
+		public const ushort RLD = 56;		
+		public const ushort SET_FL_LD = 57;
+		public const ushort SET_FL_CP = 58;
+		public const ushort SET_FL_IR = 59;
 		public const ushort I_BIT = 60;
 		public const ushort HL_BIT = 61;
-		public const ushort SET_FL_IR = 62;
+
 		
 
 		public Z80A()
@@ -576,10 +576,6 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 				case ADDS:
 					ADDS_Func(cur_instr[instr_pntr++], cur_instr[instr_pntr++], cur_instr[instr_pntr++], cur_instr[instr_pntr++]);
 					break;
-				case JAM:
-					jammed = true;
-					instr_pntr--;
-					break;
 				case EI_RETI:
 					// NOTE: This is needed for systems using multiple interrupt sources, it triggers the next interrupt
 					// Not currently implemented here
@@ -689,7 +685,6 @@ namespace BizHawk.Emulation.Cores.Components.Z80A
 			ser.Sync("instruction_pointer", ref instr_pntr);
 			ser.Sync("current instruction", ref cur_instr, false);		
 			ser.Sync("opcode", ref opcode);
-			ser.Sync("jammped", ref jammed);
 			ser.Sync("FlagI", ref FlagI);
 
 			ser.Sync("NO Preifx", ref NO_prefix);