diff --git a/src/cpu.rs b/src/cpu.rs
index 02feeec..e8a6c1a 100644
--- a/src/cpu.rs
+++ b/src/cpu.rs
@@ -12,7 +12,7 @@ use slog;
 
 #[derive(Debug)]
 pub enum CPUError {
-    UnimplementedInstruction,
+    UnimplementedInstruction(decoder::Instruction),
     OutOfBoundsException,
     UnsupportedAddress,
     DecodingError(decoder::DecodingError),
@@ -784,6 +784,13 @@ impl CPU {
                 let r = self.get_register(r);
                 self.set_clear_flag(StatusFlag::BitCopyStorage, r & (1 << *v) != 0);
             }
+            Instruction::BLD(ref r, ref v) => {
+                let mut rv = self.get_register(r);
+                if self.test_flag(StatusFlag::BitCopyStorage) {
+                    rv |= 1 << *v;
+                }
+                let r = self.set_register(r, rv);
+            }
             Instruction::SWAP(ref r) => {
                 let rv = self.get_register(r);
                 self.set_register(r, rv >> 4 | ((rv << 4) & 0xF0));
@@ -792,7 +799,7 @@ impl CPU {
                 return Err(CPUError::Breakpoint);
             }
             Instruction::NOP => {}
-            _ => return Err(CPUError::UnimplementedInstruction),
+            _ => return Err(CPUError::UnimplementedInstruction(ins)),
         }
 
         Ok(ins.cycles())
diff --git a/src/main.rs b/src/main.rs
index 391855e..97d2388 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -37,9 +37,14 @@ fn main() {
 
     let mut chip = chip::Chip::new(log.clone(), rom);
 
-    // Use GDBStub
-    info!(log, "Enabling GDB backend");
-    gdbstub::run(log.clone(), &mut chip);
+    if std::env::args().nth(2).unwrap_or("0".to_string()) == "gdb" {
+        // Use GDBStub
+        info!(log, "Enabling GDB backend");
+        gdbstub::run(log.clone(), &mut chip);
+    } else {
+        info!(log, "Running without GDB");
+        while chip.step() {}
+    }
     warn!(log, "{}", &chip.cpu);
     write_file("ram.dmp", &chip.ram).unwrap();
 }