Takes a first bash at implementing the new SCSI::Bus timing infrastructure.

Machines/Apple/Macintosh/Macintosh.cpp

@@ -75,6 +75,7 @@ template <Analyser::Static::Macintosh::Target::Model model> class ConcreteMachin
 		 	video_(audio_, drive_speed_accumulator_),
 		 	via_(via_port_handler_),
 		 	via_port_handler_(*this, clock_, keyboard_, video_, audio_, iwm_, mouse_),
+		 	scsi_bus_(CLOCK_RATE * 2),
 		 	scsi_(scsi_bus_, CLOCK_RATE * 2),
 		 	hard_drive_(scsi_bus_, 6 /* SCSI ID */),
 		 	drives_{

Storage/MassStorage/SCSI/SCSI.cpp

@@ -10,6 +10,23 @@
 
 using namespace SCSI;
 
+Bus::Bus(HalfCycles clock_rate) {
+	cycles_to_time_ = 1.0 / double(clock_rate.as_int());
+
+	// NB: note that the dispatch times below are **ORDERED**
+	// from least to greatest. Each box should contain the number
+	// of whole clock periods it will take to get the the first
+	// discrete moment after the required delay interval has been met.
+	dispatch_times_[0] = 1 + int(CableSkew / cycles_to_time_);
+	dispatch_times_[1] = 1 + int(DeskewDelay / cycles_to_time_);
+	dispatch_times_[2] = 1 + int(BusFreeDelay / cycles_to_time_);
+	dispatch_times_[3] = 1 + int(BusSettleDelay / cycles_to_time_);
+	dispatch_times_[4] = 1 + int(BusClearDelay / cycles_to_time_);
+	dispatch_times_[5] = 1 + int(BusSetDelay / cycles_to_time_);
+	dispatch_times_[6] = 1 + int(ArbitrationDelay / cycles_to_time_);
+	dispatch_times_[7] = 1 + int(ResetHoldTime / cycles_to_time_);
+}
+
 size_t Bus::add_device() {
 	const auto slot = device_states_.size();
 	device_states_.push_back(DefaultBusState);
@@ -41,9 +58,10 @@ void Bus::set_device_output(size_t device, BusState output) {
 		(state_ & Line::Request) ? 'q' : '-'
 	);
 
-	for(auto &observer: observers_) {
-		observer->scsi_bus_did_change(this, state_, 0.0);
-	}
+	bool was_asleep = preferred_clocking() == ClockingHint::Preference::None;
+	dispatch_index_ = 0;
+	time_in_state_ = HalfCycles(0);
+	if(was_asleep) update_clocking_observer();
 }
 
 BusState Bus::get_state() {
@@ -53,3 +71,29 @@ BusState Bus::get_state() {
 void Bus::add_observer(Observer *observer) {
 	observers_.push_back(observer);
 }
+
+ClockingHint::Preference Bus::preferred_clocking() {
+	return (dispatch_index_ < sizeof(dispatch_times_)) ? ClockingHint::Preference::RealTime : ClockingHint::Preference::None;
+}
+
+void Bus::run_for(HalfCycles time) {
+	if(dispatch_index_ < sizeof(dispatch_times_)) {
+		time_in_state_ += time;
+
+		const auto old_index = dispatch_index_;
+		const auto time_as_int = time_in_state_.as_int();
+		while(time_as_int >= dispatch_times_[dispatch_index_] && dispatch_index_ < sizeof(dispatch_times_)) {
+			++dispatch_index_;
+		}
+
+		if(dispatch_index_ != old_index) {
+			for(auto &observer: observers_) {
+				observer->scsi_bus_did_change(this, state_, double(time_as_int) * cycles_to_time_);
+			}
+		}
+
+		if(preferred_clocking() == ClockingHint::Preference::None) {
+			update_clocking_observer();
+		}
+	}
+}

Storage/MassStorage/SCSI/SCSI.hpp

@@ -57,6 +57,9 @@ enum Line: BusState {
 #define us(x)	(x) / 1000000.0
 #define ns(x)	(x) / 1000000000.0
 
+/// The minimum amount of time that reset must be held for.
+constexpr double ResetHoldTime		= us(25.0);
+
 /// The minimum amount of time a SCSI device must wait after asserting ::Busy
 /// until the data bus can be inspected to see whether arbitration has been won.
 constexpr double ArbitrationDelay	= us(1.7);
@@ -81,9 +84,6 @@ constexpr double BusFreeDelay		= ns(100.0);
 /// The minimum amount of time required for deskew of "certain signals". TODO: which?
 constexpr double DeskewDelay		= ns(45.0);
 
-/// The minimum amount of time that reset must be held for.
-constexpr double ResetHoldTime		= us(25.0);
-
 /// The maximum amount of time that propagation of a SCSI bus signal can take between
 /// any two devices.
 constexpr double CableSkew			= ns(10.0);
@@ -91,8 +91,9 @@ constexpr double CableSkew			= ns(10.0);
 #undef ns
 #undef us
 
-class Bus {
+class Bus: public ClockingHint::Source {
 	public:
+		Bus(HalfCycles clock_rate);
 
 		/*!
 			Adds a device to the bus, returning the index it should use
@@ -123,7 +124,22 @@ class Bus {
 		*/
 		void add_observer(Observer *);
 
+		/*!
+			SCSI buses don't have a clock. But devices on the bus are concerned with time-based factors,
+			and `run_for` is the way that time propagates within this emulator. So please permit this
+			fiction.
+		*/
+		void run_for(HalfCycles);
+
+		/// As per ClockingHint::Source.
+		ClockingHint::Preference preferred_clocking() final;
+
 	private:
+		HalfCycles time_in_state_;
+		double cycles_to_time_ = 1.0;
+		size_t dispatch_index_ = 0;
+		int dispatch_times_[8];
+
 		std::vector<BusState> device_states_;
 		BusState state_ = DefaultBusState;
 		std::vector<Observer *> observers_;