diff --git a/cpu/ppc/ppcexec.cpp b/cpu/ppc/ppcexec.cpp
index 3248165486..2a1371b120 100644
--- a/cpu/ppc/ppcexec.cpp
+++ b/cpu/ppc/ppcexec.cpp
@@ -275,6 +275,17 @@ PPCOpcode* ppc_opcode_grabber = OpcodeGrabberNoFPU;
 /** Exception helpers. */
 
 void ppc_illegalop(uint32_t opcode) {
+    // Zero values are used as sentinels in the TNT ROM and are thus somewhat
+    // common, don't log them.
+    if (opcode) {
+        PPCDisasmContext ctx;
+        ctx.instr_code = opcode;
+        ctx.instr_addr = 0;
+        ctx.simplified = false;
+        auto op_name = disassemble_single(&ctx);
+        LOG_F(WARNING, "Illegal opcode exception raised for 0x%08x (decoded as %s). The PC was 0x%08x.", opcode, op_name.c_str(), ppc_state.pc);
+    }
+
     ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
 }
 
diff --git a/cpu/ppc/ppcfpopcodes.cpp b/cpu/ppc/ppcfpopcodes.cpp
index 88263b0faf..d62deb9b5f 100644
--- a/cpu/ppc/ppcfpopcodes.cpp
+++ b/cpu/ppc/ppcfpopcodes.cpp
@@ -1025,7 +1025,7 @@ void dppc_interpreter::ppc_lfsu(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1046,7 +1046,7 @@ void dppc_interpreter::ppc_lfsux(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
         return;
     }
 }
@@ -1070,7 +1070,7 @@ void dppc_interpreter::ppc_lfdu(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1091,7 +1091,7 @@ void dppc_interpreter::ppc_lfdux(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1114,7 +1114,7 @@ void dppc_interpreter::ppc_stfsu(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1135,7 +1135,7 @@ void dppc_interpreter::ppc_stfsux(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1156,7 +1156,7 @@ void dppc_interpreter::ppc_stfdu(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1175,7 +1175,7 @@ void dppc_interpreter::ppc_stfdux(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ea);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
diff --git a/cpu/ppc/ppcmmu.cpp b/cpu/ppc/ppcmmu.cpp
index 765b51a30b..09c434a752 100644
--- a/cpu/ppc/ppcmmu.cpp
+++ b/cpu/ppc/ppcmmu.cpp
@@ -1088,7 +1088,7 @@ static void mpc601_bat_update(uint32_t bat_reg)
 
 static void mpc601_dbat_update(uint32_t /*bat_reg*/)
 {
-    // ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+    // ppc_illegalop(opcode);
 }
 
 static void ppc_ibat_update(uint32_t bat_reg)
diff --git a/cpu/ppc/ppcopcodes.cpp b/cpu/ppc/ppcopcodes.cpp
index 9fc410d9a1..3faeaa7713 100644
--- a/cpu/ppc/ppcopcodes.cpp
+++ b/cpu/ppc/ppcopcodes.cpp
@@ -1002,14 +1002,14 @@ void dppc_interpreter::ppc_mfspr(uint32_t opcode) {
     switch (ref_spr) {
     case SPR::MQ:
         if (!(is_601 || include_601)) {
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
             return;
         }
         ppc_state.gpr[reg_d] = ppc_state.spr[ref_spr];
         break;
     case SPR::RTCL_U:
         if (!is_601) {
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
             return;
         }
         calc_rtcl_value();
@@ -1019,7 +1019,7 @@ void dppc_interpreter::ppc_mfspr(uint32_t opcode) {
         break;
     case SPR::RTCU_U:
         if (!is_601) {
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
             return;
         }
         calc_rtcl_value();
@@ -1029,7 +1029,7 @@ void dppc_interpreter::ppc_mfspr(uint32_t opcode) {
         break;
     case SPR::DEC_U:
         if (!is_601) {
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
             return;
         }
         // fallthrough
@@ -1093,13 +1093,13 @@ void dppc_interpreter::ppc_mtspr(uint32_t opcode) {
         if (is_601 || include_601)
             ppc_state.spr[ref_spr] = val;
         else
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
         break;
     case SPR::RTCL_U:
     case SPR::RTCU_U:
     case SPR::DEC_U:
         if (!is_601) {
-            ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+            ppc_illegalop(opcode);
         }
         break;
     case SPR::XER:
@@ -1214,7 +1214,7 @@ void dppc_interpreter::ppc_mftb(uint32_t opcode) {
         ppc_state.spr[TBL_S] = uint32_t(tbr_value);
         break;
     default:
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
      }
 }
 
@@ -1700,14 +1700,16 @@ void dppc_interpreter::ppc_stu(uint32_t opcode) {
 #endif
     ppc_grab_regssa(opcode);
 
-    if (reg_a != 0) {
+    // MPC601 permits RA=0 for POWER compatibility and suppresses the update.
+    if (reg_a != 0 || is_601) {
         uint32_t ea = int32_t(int16_t(opcode));
-        ea += ppc_result_a;
+        ea += reg_a ? ppc_result_a : 0;
         mmu_write_vmem<T>(opcode, ea, ppc_result_d);
-        ppc_state.gpr[reg_a] = ea;
+        if (reg_a != 0)
+            ppc_state.gpr[reg_a] = ea;
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 
 }
@@ -1723,13 +1725,15 @@ void dppc_interpreter::ppc_stux(uint32_t opcode) {
 #endif
     ppc_grab_regssab(opcode);
 
-    if (reg_a != 0) {
-        uint32_t ea = ppc_result_a + ppc_result_b;
+    // MPC601 permits RA=0 for POWER compatibility and suppresses the update.
+    if (reg_a != 0 || is_601) {
+        uint32_t ea = (reg_a ? ppc_result_a : 0) + ppc_result_b;
         mmu_write_vmem<T>(opcode, ea, ppc_result_d);
-        ppc_state.gpr[reg_a] = ea;
+        if (reg_a != 0)
+            ppc_state.gpr[reg_a] = ea;
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1821,7 +1825,7 @@ void dppc_interpreter::ppc_lzu(uint32_t opcode) {
         ppc_result_a = ea;
         ppc_store_iresult_reg(reg_a, ppc_result_a);
     } else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1857,7 +1861,7 @@ void dppc_interpreter::ppc_lzux(uint32_t opcode) {
         ppc_result_a = ea;
         ppc_store_iresult_reg(reg_a, ppc_result_a);
     } else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1889,7 +1893,7 @@ void dppc_interpreter::ppc_lhau(uint32_t opcode) {
         ppc_result_a = ea;
         ppc_store_iresult_reg(reg_a, ppc_result_a);
     } else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -1906,7 +1910,7 @@ void dppc_interpreter::ppc_lhaux(uint32_t opcode) {
         ppc_store_iresult_reg(reg_a, ppc_result_a);
     }
     else {
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 }
 
@@ -2014,7 +2018,7 @@ void dppc_interpreter::ppc_lswx(uint32_t opcode) {
     if ((reg_d == 0 && reg_a == 0) || (reg_d == reg_a) || (reg_d == reg_b)) {
         // UNTESTED! Does invalid form really cause exception?
         // G4 doesn't do exception
-        ppc_exception_handler(Except_Type::EXC_PROGRAM, Exc_Cause::ILLEGAL_OP);
+        ppc_illegalop(opcode);
     }
 */