diff --git a/Analyser/Static/Commodore/StaticAnalyser.cpp b/Analyser/Static/Commodore/StaticAnalyser.cpp
index 52c3bb73b..066a0c105 100644
--- a/Analyser/Static/Commodore/StaticAnalyser.cpp
+++ b/Analyser/Static/Commodore/StaticAnalyser.cpp
@@ -209,10 +209,6 @@ Analyser::Static::TargetList Analyser::Static::Commodore::GetTargets(
 	// Inspect discovered files to try to divine machine and memory model.
 	auto vic_memory_model = Target::MemoryModel::Unexpanded;
 
-	if(files.size() > 1) {
-		printf("");
-	}
-
 	auto it = files.begin();
 	while(it != files.end()) {
 		const auto &file = *it;
diff --git a/Machines/Commodore/1540/Implementation/C1540.cpp b/Machines/Commodore/1540/Implementation/C1540.cpp
index ee7038f85..6a1b066c1 100644
--- a/Machines/Commodore/1540/Implementation/C1540.cpp
+++ b/Machines/Commodore/1540/Implementation/C1540.cpp
@@ -153,11 +153,11 @@ void MachineBase::process_index_hole()	{}
 
 // MARK: - Drive VIA delegate
 
-void MachineBase::drive_via_did_step_head(void *, int direction) {
+void MachineBase::drive_via_did_step_head(void *, const int direction) {
 	get_drive().step(Storage::Disk::HeadPosition(direction, 2));
 }
 
-void MachineBase::drive_via_did_set_data_density(void *, int density) {
+void MachineBase::drive_via_did_set_data_density(void *, const int density) {
 	set_expected_bit_length(Storage::Encodings::CommodoreGCR::length_of_a_bit_in_time_zone(unsigned(density)));
 }
 
@@ -240,22 +240,22 @@ void DriveVIA::set_control_line_output(MOS::MOS6522::Port port, MOS::MOS6522::Li
 void DriveVIA::set_port_output(MOS::MOS6522::Port port, uint8_t value, uint8_t) {
 	if(port) {
 		if(previous_port_b_output_ != value) {
-			// record drive motor state
+			// Record drive motor state.
 			drive_motor_ = value&4;
 
-			// check for a head step
-			int step_difference = ((value&3) - (previous_port_b_output_&3))&3;
+			// Check for a head step.
+			const int step_difference = ((value&3) - (previous_port_b_output_&3))&3;
 			if(step_difference) {
 				if(delegate_) delegate_->drive_via_did_step_head(this, (step_difference == 1) ? 1 : -1);
 			}
 
-			// check for a change in density
-			int density_difference = (previous_port_b_output_^value) & (3 << 5);
+			// Check for a change in density.
+			const int density_difference = (previous_port_b_output_^value) & (3 << 5);
 			if(density_difference && delegate_) {
 				delegate_->drive_via_did_set_data_density(this, (value >> 5)&3);
 			}
 
-			// post the LED status
+			// Post the LED status.
 			if(observer_) observer_->set_led_status("Drive", value&8);
 
 			previous_port_b_output_ = value;
diff --git a/Machines/Commodore/Plus4/Plus4.cpp b/Machines/Commodore/Plus4/Plus4.cpp
index 3c5a3b59a..81b9953c8 100644
--- a/Machines/Commodore/Plus4/Plus4.cpp
+++ b/Machines/Commodore/Plus4/Plus4.cpp
@@ -162,7 +162,7 @@ public:
 		if(has_c1541) {
 			c1541_ = std::make_unique<Commodore::C1540::Machine>(Commodore::C1540::Personality::C1541, roms);
 			c1541_->set_serial_bus(serial_bus_);
-			serial_port_.set_bus(serial_bus_);
+			Commodore::Serial::attach(serial_port_, serial_bus_);
 		}
 
 		tape_player_ = std::make_unique<Storage::Tape::BinaryTapePlayer>(clock);
@@ -215,29 +215,33 @@ public:
 					*value = io_direction_;
 				} else {
 					const uint8_t all_inputs =
-						(tape_player_->input() ? 0x00 : 0x10) |
+						(tape_player_->input() ? 0x10 : 0x00) |
 						(serial_port_.level(Commodore::Serial::Line::Data) ? 0x80 : 0x00) |
 						(serial_port_.level(Commodore::Serial::Line::Clock) ? 0x40 : 0x00);
 					*value =
 						(io_direction_ & io_output_) |
 						((~io_direction_) & all_inputs);
-					printf("[%04x] In: %02x\n", m6502_.value_of(CPU::MOS6502::Register::ProgramCounter), *value);
+//					printf("[%04x] In: %02x\n", m6502_.value_of(CPU::MOS6502::Register::ProgramCounter), *value);
+//					printf("Input: %02x\n", *value);
 				}
 			} else {
 				if(!address) {
 					io_direction_ = *value;
+//					printf("Direction: %02x\n", io_direction_);
 				} else {
 					io_output_ = *value;
+//					printf("'Output': %02x\n", io_output_);
 				}
 
-				const auto output = io_output_ & ~io_direction_;
-				tape_player_->set_motor_control(!(output & 0x08));
+				const auto output = io_output_ | ~io_direction_;
+//				printf("Visible output: %02x\n\n", uint8_t(output));
+				tape_player_->set_motor_control(~output & 0x08);
 				serial_port_.set_output(
-					Commodore::Serial::Line::Data, Commodore::Serial::LineLevel(~output & 0x01));
+					Commodore::Serial::Line::Data, Commodore::Serial::LineLevel(output & 0x01));
 				serial_port_.set_output(
-					Commodore::Serial::Line::Clock, Commodore::Serial::LineLevel(~output & 0x02));
+					Commodore::Serial::Line::Clock, Commodore::Serial::LineLevel(output & 0x02));
 				serial_port_.set_output(
-					Commodore::Serial::Line::Attention, Commodore::Serial::LineLevel(~output & 0x04));
+					Commodore::Serial::Line::Attention, Commodore::Serial::LineLevel(output & 0x04));
 			}
 
 //			printf("%04x: %02x %c\n", address, *value, isReadOperation(operation) ? 'r' : 'w');