Adopt granular flushing widely.

Machines/Amiga/Amiga.cpp

@@ -176,10 +176,6 @@ class ConcreteMachine:
 			return total_length - cycle.length;
 		}
 
-		void flush() {
-			chipset_.flush();
-		}
-
 	private:
 		CPU::MC68000Mk2::Processor<ConcreteMachine, true, true> mc68000_;
 
@@ -220,7 +216,7 @@ class ConcreteMachine:
 		}
 
 		void flush_output(Output) final {
-			flush();
+			chipset_.flush();
 		}
 
 		// MARK: - MachineTypes::MouseMachine.

Machines/AmstradCPC/AmstradCPC.cpp

@@ -1048,11 +1048,15 @@ template <bool has_fdc> class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		/// Another Z80 entry point; indicates that a partcular run request has concluded.
-		void flush() {
+		/// Fields requests to pump all output.
+		void flush_output(Output output) final {
 			// Just flush the AY.
-			ay_.update();
-			ay_.flush();
+			if(int(output) & int(Output::Audio)) {
+				ay_.update();
+				ay_.flush();
+			}
+
+			// Always flush the FDC.
 			flush_fdc();
 		}
 

Machines/Apple/AppleII/AppleII.cpp

@@ -810,11 +810,16 @@ template <Analyser::Static::AppleII::Target::Model model> class ConcreteMachine:
 			return Cycles(1);
 		}
 
-		void flush() {
-			update_video();
-			update_audio();
+		void flush_output(Output output) final {
 			update_just_in_time_cards();
-			audio_queue_.perform();
+
+			if(int(output) & int(Output::Video)) {
+				update_video();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 		void run_for(const Cycles cycles) final {

Machines/Apple/AppleIIgs/AppleIIgs.cpp

@@ -326,13 +326,17 @@ class ConcreteMachine:
 			m65816_.run_for(cycles);
 		}
 
-		void flush() {
-			video_.flush();
+		void flush_output(Output output) final {
 			iwm_.flush();
 			adb_glu_.flush();
 
-			AudioUpdater updater(this);
-			audio_queue_.perform();
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				AudioUpdater updater(this);
+				audio_queue_.perform();
+			}
 		}
 
 		void set_scan_target(Outputs::Display::ScanTarget *target) override {

Machines/Apple/Macintosh/Macintosh.cpp

@@ -190,7 +190,6 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 
 		void run_for(const Cycles cycles) final {
 			mc68000_.run_for(cycles);
-			flush();
 		}
 
 		using Microcycle = CPU::MC68000Mk2::Microcycle;
@@ -366,7 +365,7 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 			return delay;
 		}
 
-		void flush() {
+		void flush_output(Output) {
 			// Flush the video before the audio queue; in a Mac the
 			// video is responsible for providing part of the
 			// audio signal, so the two aren't as distinct as in

Machines/Atari/2600/Atari2600.cpp

@@ -174,7 +174,7 @@ class ConcreteMachine:
 			bus_->apply_confidence(confidence_counter_);
 		}
 
-		void flush() {
+		void flush_output(Output) final {
 			bus_->flush();
 		}
 

Machines/Atari/ST/AtariST.cpp

@@ -154,7 +154,6 @@ class ConcreteMachine:
 			}
 
 			mc68000_.run_for(cycles);
-			flush();
 		}
 
 		// MARK: MC68000::BusHandler
@@ -414,14 +413,19 @@ class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		void flush() {
+		void flush_output(Output output) final {
 			dma_.flush();
 			mfp_.flush();
 			keyboard_acia_.flush();
 			midi_acia_.flush();
-			video_.flush();
-			update_audio();
-			audio_queue_.perform();
+
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 	private:

Machines/ColecoVision/ColecoVision.cpp

@@ -342,10 +342,14 @@ class ConcreteMachine:
 			return penalty;
 		}
 
-		void flush() {
-			vdp_.flush();
-			update_audio();
-			audio_queue_.perform();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				vdp_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 		float get_confidence() final {

Machines/Commodore/Vic-20/Vic20.cpp

@@ -620,9 +620,13 @@ class ConcreteMachine:
 			return Cycles(1);
 		}
 
-		void flush() {
-			update_video();
-			mos6560_.flush();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				update_video();
+			}
+			if(int(output) & int(Output::Audio)) {
+				mos6560_.flush();
+			}
 		}
 
 		void run_for(const Cycles cycles) final {

Machines/Electron/Electron.cpp

@@ -501,10 +501,14 @@ template <bool has_scsi_bus> class ConcreteMachine:
 			return Cycles(int(cycles));
 		}
 
-		forceinline void flush() {
-			video_.flush();
-			update_audio();
-			audio_queue_.perform();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 		void set_scan_target(Outputs::Display::ScanTarget *scan_target) final {

Machines/Enterprise/Enterprise.cpp

@@ -539,10 +539,14 @@ template <bool has_disk_controller, bool is_6mhz> class ConcreteMachine:
 			return penalty;
 		}
 
-		void flush() {
-			nick_.flush();
-			update_audio();
-			audio_queue_.perform();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				nick_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 	private:

Machines/MSX/MSX.cpp

@@ -615,10 +615,14 @@ class ConcreteMachine:
 			return addition;
 		}
 
-		void flush() {
-			vdp_.flush();
-			update_audio();
-			audio_queue_.perform();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				vdp_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 		}
 
 		void set_keyboard_line(int line) {

Machines/MasterSystem/MasterSystem.cpp

@@ -392,9 +392,6 @@ class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		void flush() {
-		}
-
 		const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() final {
 			return joysticks_;
 		}

Machines/Oric/Oric.cpp

@@ -578,9 +578,13 @@ template <Analyser::Static::Oric::Target::DiskInterface disk_interface, CPU::MOS
 			return Cycles(1);
 		}
 
-		forceinline void flush() {
-			video_.flush();
-			via_.flush();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+			if(int(output) & int(Output::Audio)) {
+				via_.flush();
+			}
 			diskii_.flush();
 		}
 

Machines/Sinclair/ZX8081/ZX8081.cpp

@@ -292,11 +292,16 @@ template<bool is_zx81> class ConcreteMachine:
 			return HalfCycles(0);
 		}
 
-		forceinline void flush() {
-			video_.flush();
+		void flush_output(Output output) final {
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+
 			if constexpr (is_zx81) {
-				update_audio();
-				audio_queue_.perform();
+				if(int(output) & int(Output::Audio)) {
+					update_audio();
+					audio_queue_.perform();
+				}
 			}
 		}
 

Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp

@@ -263,10 +263,15 @@ template<Model model> class ConcreteMachine:
 			}
 		}
 
-		void flush() {
-			video_.flush();
-			update_audio();
-			audio_queue_.perform();
+		void flush_output(Output output) override {
+			if(int(output) & int(Output::Video)) {
+				video_.flush();
+			}
+
+			if(int(output) & int(Output::Audio)) {
+				update_audio();
+				audio_queue_.perform();
+			}
 
 			if constexpr (model == Model::Plus3) {
 				fdc_.flush();