diff --git a/src/interpreter/computer.rs b/src/interpreter/computer.rs
index c2a1618..3487113 100644
--- a/src/interpreter/computer.rs
+++ b/src/interpreter/computer.rs
@@ -110,6 +110,20 @@ impl Computer {
         self.op(op, flag_set, false, dest, src);
     }
 
+    /// Perform test operation, which acts like [`Self::and()`], but without
+    /// saving the result and only setting [`Self::flags`].
+    pub fn test(&mut self, dest: ModRmTarget, src: Operand) {
+        let op: fn(Lhs, Rhs) -> ArithmeticResult = |lhs, rhs| lhs & rhs;
+        let flag_set: fn(&mut Flags, ArithmeticResult, Lhs, Rhs) = |flags, result, _, _| {
+            flags.cf = false;
+            flags.of = false;
+            flags.zf = result.zero();
+            flags.sf = result.msb();
+            flags.pf = result.parity();
+        };
+        self.op(op, flag_set, false, dest, src);
+    }
+
     /// Perform `dest` = `dest` + `src` + CF. Sets flags.
     pub fn adc(&mut self, dest: ModRmTarget, src: Operand) {
         let cf = self.flags.cf as u8;
diff --git a/src/interpreter/interpreter.rs b/src/interpreter/interpreter.rs
index 279feef..ec705a3 100644
--- a/src/interpreter/interpreter.rs
+++ b/src/interpreter/interpreter.rs
@@ -3,7 +3,7 @@ use std::{fmt::Debug, process::exit};
 
 use crate::{
     instructions::{Instruction, Mnemonic},
-    interpreter::interrupt::Mess1,
+    interpreter::{interrupt::Mess1, memory::Memory},
     operands::{Byte, ImmediateOperand, ModRmTarget},
 };
 
@@ -366,10 +366,40 @@ impl Interpreter {
                 /*
                  * Test
                  */
+                Mnemonic::TEST(dest, src) => self
+                    .computer
+                    .test(dest, Operand::ModRmTarget(ModRmTarget::Register(src))),
+                Mnemonic::TEST_Ib(dest, src) => self
+                    .computer
+                    .test(dest, Operand::Immediate(ImmediateOperand::Byte(src))),
+                Mnemonic::TEST_Iv(dest, src) => self
+                    .computer
+                    .test(dest, Operand::Immediate(ImmediateOperand::Word(src))),
+                Mnemonic::TEST_ALIb(src_byte) => self.computer.test(
+                    ModRmTarget::Register(crate::register::Register::AL),
+                    Operand::Immediate(ImmediateOperand::Byte(src_byte)),
+                ),
+                Mnemonic::TEST_AXIv(src_word) => self.computer.test(
+                    ModRmTarget::Register(crate::register::Register::AX),
+                    Operand::Immediate(ImmediateOperand::Word(src_word)),
+                ),
 
                 /*
                  * XCHG
                  */
+                Mnemonic::XCHG(target, reg) => {
+                    let tmp = self.computer.read_modrm(target);
+                    self.computer
+                        .write_modrm(target, self.computer.regs.read(reg));
+                    self.computer.regs.write(reg, tmp);
+                }
+                Mnemonic::XCHG_AX(reg) => {
+                    let tmp = self.computer.regs.read(reg);
+                    self.computer
+                        .regs
+                        .write(reg, self.computer.regs.ax.read().into());
+                    self.computer.regs.write(reg, tmp);
+                }
 
                 /*
                  * MOV
@@ -411,14 +441,37 @@ impl Interpreter {
                 /*
                  * LEA
                  */
+                Mnemonic::LEA(target, reg) => {
+                    let val = match target {
+                        ModRmTarget::Memory(idx) => Memory::calc_memidx(&self.computer.regs, idx),
+                        ModRmTarget::Register(reg) => self.computer.regs.read(reg),
+                    };
+                    self.computer.regs.write(reg, val);
+                }
 
                 /*
                  * Sign extensions
                  */
+                Mnemonic::CBW => {
+                    if ImmediateOperand::Byte(self.computer.regs.ax.lower).msb() {
+                        // extend sign bit into AX, i.e. all bits set
+                        self.computer.regs.ax.upper = 0xff;
+                    }
+                }
+                Mnemonic::CWD => {
+                    if ImmediateOperand::Word(self.computer.regs.ax.read()).msb() {
+                        // extend sign bit into DX, i.e. all bits set
+                        self.computer.regs.dx.write(0xffff);
+                    }
+                }
 
                 /*
                  * Wait
                  */
+                Mnemonic::WAIT => {
+                    log::info!("wait");
+                    continue;
+                }
 
                 /*
                  * Push/Pop Flags
@@ -439,6 +492,14 @@ impl Interpreter {
                 /*
                  * Not/Neg
                  */
+                Mnemonic::NOT(target) => {
+                    self.computer
+                        .write_modrm(target, !self.computer.read_modrm(target));
+                }
+                Mnemonic::NEG(target) => {
+                    let val = !self.computer.read_modrm(target);
+                    self.computer.write_modrm(target, val + 0b1);
+                }
 
                 /*
                  * MUL
@@ -451,6 +512,10 @@ impl Interpreter {
                 /*
                  * HLT
                  */
+                Mnemonic::HLT => {
+                    eprintln!("Processor halted... exiting.");
+                    exit(1);
+                }
 
                 /*
                  * Shift and Rotate
@@ -472,6 +537,13 @@ impl Interpreter {
                 /*
                  * Flag manipulation
                  */
+                Mnemonic::CLC => self.computer.flags.cf = false,
+                Mnemonic::STC => self.computer.flags.cf = true,
+                Mnemonic::CLI => self.computer.flags.r#if = false,
+                Mnemonic::STI => self.computer.flags.r#if = true,
+                Mnemonic::CLD => self.computer.flags.df = false,
+                Mnemonic::STD => self.computer.flags.df = true,
+                Mnemonic::CMC => self.computer.flags.cf = !self.computer.flags.cf,
 
                 /*
                  * Repeat prefixes
@@ -484,6 +556,10 @@ impl Interpreter {
                 /*
                  * Misc
                  */
+                Mnemonic::LOCK => {
+                    log::info!("lock#");
+                    continue;
+                }
                 _ => log::info!("no action done"),
             }
         }
diff --git a/src/interpreter/memory.rs b/src/interpreter/memory.rs
index 2578f17..c13c447 100644
--- a/src/interpreter/memory.rs
+++ b/src/interpreter/memory.rs
@@ -66,8 +66,8 @@ impl Memory {
         }
     }
 
-    /// Calculate the absolute Memory Index from a [`MemoryIndex`] struct.
-    fn calc_memidx(
+    /// Calculate the absolute memory address from a [`MemoryIndex`] struct.
+    pub fn calc_memidx(
         regs: &crate::interpreter::register::Register,
         idx: MemoryIndex,
     ) -> ImmediateOperand {
diff --git a/src/operands.rs b/src/operands.rs
index 109ef66..7185748 100644
--- a/src/operands.rs
+++ b/src/operands.rs
@@ -7,7 +7,7 @@ use crate::register::SegmentRegister;
 
 use crate::{disasm::DisasmError, register::Register};
 use core::fmt;
-use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Sub};
+use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Not, Sub};
 
 pub type Byte = u8; // b
 pub type IByte = i8; // used for displacements of memory access
@@ -334,6 +334,17 @@ impl BitXor for ImmediateOperand {
     }
 }
 
+impl Not for ImmediateOperand {
+    type Output = Self;
+
+    fn not(self) -> Self::Output {
+        match self {
+            ImmediateOperand::Byte(b) => ImmediateOperand::Byte(!b),
+            ImmediateOperand::Word(w) => ImmediateOperand::Word(!w),
+        }
+    }
+}
+
 impl fmt::Display for ImmediateOperand {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {