diff --git a/simulator/mips/mips_instr.cpp b/simulator/mips/mips_instr.cpp
index db80e9c6f..6eab2ead3 100644
--- a/simulator/mips/mips_instr.cpp
+++ b/simulator/mips/mips_instr.cpp
@@ -294,6 +294,50 @@ BaseMIPSInstr<RegisterUInt>::BaseMIPSInstr( MIPSVersion version, uint32 bytes, A
     }
 }
 
+template<typename RegisterUInt>
+BaseMIPSInstr<RegisterUInt>::BaseMIPSInstr( MIPSVersion version, std::string_view str_opcode, Addr PC) :
+    new_PC( PC + 4),
+    PC( PC)
+{
+    auto it = find_entry( isaMapR,      str_opcode);
+    if ( it == isaMapR.end())
+        it =  find_entry( isaMapRI,     str_opcode);
+    if ( it == isaMapRI.end())
+        it =  find_entry( isaMapMIPS32, str_opcode);
+    if ( it == isaMapMIPS32.end())
+        it =  find_entry( isaMapIJ,     str_opcode);
+    
+    if ( str_opcode == "nop")
+    {
+        init (isaMapR.find( 0)->second, version);
+        disasm = "nop ";
+    }
+    else if ( it == isaMapIJ.end())
+    {
+        std::ostringstream oss;
+        if ( PC != 0)
+            oss << std::hex << "0x" << PC << ": ";
+        oss << str_opcode << '\t' << "Unknown";
+        disasm = oss.str();
+    }
+    else {
+        init( it->second, version);
+    } 
+}
+
+template<typename RegisterUInt>
+typename BaseMIPSInstr<RegisterUInt>::MapType::const_iterator 
+BaseMIPSInstr<RegisterUInt>::find_entry( const BaseMIPSInstr<RegisterUInt>::MapType& map, std::string_view name) const
+{
+    auto it = map.begin();
+    for ( ; it != map.end(); it++)
+    {
+        if ( it->second.name == name)
+            return it;
+    }
+    return map.end();
+}
+
 template<typename RegisterUInt>
 MIPSRegister BaseMIPSInstr<RegisterUInt>::get_register( RegType type) const
 {
diff --git a/simulator/mips/mips_instr.h b/simulator/mips/mips_instr.h
index d4e2e2cf6..61f7b3101 100644
--- a/simulator/mips/mips_instr.h
+++ b/simulator/mips/mips_instr.h
@@ -161,6 +161,7 @@ class BaseMIPSInstr
         static const MapType isaMapRI;
         static const MapType isaMapIJ;
         static const MapType isaMapMIPS32;
+        typename MapType::const_iterator find_entry( const MapType& isaMap, std::string_view name) const;
 
         MIPSRegister src1 = MIPSRegister::zero;
         MIPSRegister src2 = MIPSRegister::zero;
@@ -402,6 +403,7 @@ class BaseMIPSInstr
         Execute function = &BaseMIPSInstr::execute_unknown;
     protected:
         BaseMIPSInstr( MIPSVersion version, uint32 bytes, Addr PC);
+        BaseMIPSInstr( MIPSVersion version, std::string_view str_opcode, Addr PC);
     public:
         static const constexpr Endian endian = Endian::little;
     
@@ -467,6 +469,9 @@ class BaseMIPSInstr
         Trap trap_type() const { return trap; }
 
         bool is_bubble() const { return is_nop() && PC == 0; }
+        
+        void set_v_imm( uint32 value) { v_imm = value; }
+        auto get_v_imm() { return v_imm; }
 
         void set_v_src( RegisterUInt value, uint8 index)
         {
@@ -511,6 +516,8 @@ class MIPSInstr : public BaseMIPSInstr<MIPSRegisterUInt<V>>
 public:
     explicit MIPSInstr( uint32 bytes, Addr PC = 0)
         : Base( V, bytes, PC) { }
+    explicit MIPSInstr( std::string_view str_opcode, Addr PC = 0)
+        : Base( V, str_opcode, PC) { }
 };
 
 
diff --git a/simulator/mips/t/unit_test.cpp b/simulator/mips/t/unit_test.cpp
index 039746b8f..733f0925b 100644
--- a/simulator/mips/t/unit_test.cpp
+++ b/simulator/mips/t/unit_test.cpp
@@ -9,6 +9,49 @@ TEST_CASE( "MIPS32_instr_init: Process_Wrong_Args_Of_Constr")
     CHECK_NOTHROW( MIPS32Instr(0x0).execute());
 }
 
+TEST_CASE( "MIPS32_instr: invalid instruction in ctor from string")
+{
+    MIPS32Instr instr( "invalid_instruction");
+    CHECK_THROWS_AS( instr.execute(), UnknownMIPSInstruction);
+}
+
+TEST_CASE( "MIPS32_instr: sllv")
+{
+    MIPS32Instr instr( "sllv");
+    instr.set_v_src( 1, 0);
+    instr.set_v_src( 0, 1);
+    instr.execute();
+    CHECK( instr.get_v_dst() == 1);
+}
+
+TEST_CASE( "MIPS32_instr: mul")
+{
+    MIPS32Instr instr( "mul");
+    instr.set_v_src( 10, 0);
+    instr.set_v_src( 20, 1);
+    instr.execute();
+    CHECK( instr.get_v_dst() == 200);
+}
+
+TEST_CASE( "MIPS32_instr: addi")
+{
+    MIPS32Instr instr( "addi");
+    instr.set_v_src( 10, 0);
+    instr.set_v_src( 0, 1);
+    instr.set_v_imm( 20);
+    instr.execute();
+    CHECK( instr.get_v_dst() == 30);
+}
+
+TEST_CASE( "MIPS32_instr: teqi")
+{
+    MIPS32Instr instr( "teqi");
+    instr.set_v_src( 0, 0);
+    instr.set_v_imm( 0);
+    instr.execute();
+    CHECK( instr.has_trap());
+}
+
 TEST_CASE( "MIPS32_instr: Divmult")
 {
     CHECK(MIPS32Instr(0x02290018).is_divmult());
@@ -19,6 +62,14 @@ TEST_CASE( "MIPS32_instr: Divmult")
     CHECK(MIPS32Instr(0x72290001).is_divmult());
     CHECK(MIPS32Instr(0x72290004).is_divmult());
     CHECK(MIPS32Instr(0x72290005).is_divmult());
+    CHECK(MIPS32Instr("mult").is_divmult());
+    CHECK(MIPS32Instr("multu").is_divmult());
+    CHECK(MIPS32Instr("div").is_divmult());
+    CHECK(MIPS32Instr("divu").is_divmult());
+    CHECK(MIPS32Instr("dmult").is_divmult());
+    CHECK(MIPS32Instr("dmultu").is_divmult());
+    CHECK(MIPS32Instr("ddiv").is_divmult());
+    CHECK(MIPS32Instr("ddivu").is_divmult());
 }
     
 TEST_CASE( "MIPS32_instr_disasm: Process_Disasm_R")
@@ -79,6 +130,7 @@ TEST_CASE( "MIPS32_instr_disasm: Process_Disasm_R")
     CHECK(MIPS32Instr(0x02290036).get_disasm() == "tne $s1, $t1");
     CHECK(MIPS32Instr(0x01208809).get_disasm() == "jalr $s1, $t1");
     CHECK(MIPS32Instr(0x00000000).get_disasm() == "nop ");
+    CHECK(MIPS32Instr     ("nop").get_disasm() == "nop ");
 }
 
 TEST_CASE( "MIPS32_instr_disasm: Process_Disasm_IJ")