diff --git a/Machines/Tandy/CoCo/CoCo.cpp b/Machines/Tandy/CoCo/CoCo.cpp
index f9fa7e0ab..f1e6e30b7 100644
--- a/Machines/Tandy/CoCo/CoCo.cpp
+++ b/Machines/Tandy/CoCo/CoCo.cpp
@@ -482,11 +482,9 @@ public:
 		bus_phase_ &= 1;
 
 		if constexpr (has_disk_drive) {
-			// Piggy-back off the existing bus_phase_ counter to multiply the clock by 4.5,
-			// giving very close to the standard 8Mhz. Unless and until a real clock speed emerges.
-			disk_controller_.run_for(
-				duration * 4 + bus_phase_
-			);
+			// Multiply by 4.5 to get very close to 8Mhz for the controller.
+			cycles_16mhz_ += duration * 9;
+			disk_controller_.run_for(cycles_16mhz_.divide(2));
 		}
 
 		if(m6847_ += duration) {
@@ -1012,11 +1010,18 @@ private:
 			tape_player_.set_tape(media.tapes.front(), TargetPlatform::ThomsonMO);
 		}
 
+		if(has_disk_drive && !media.disks.empty()) {
+			for(size_t c = 0; c < media.disks.size() && c < 4; c++) {
+				disk_controller_.set_disk(media.disks[c], c);
+			}
+		}
+
 		const bool had_cartridge =
+			!has_disk_drive &&
 			!media.cartridges.empty() &&
 			sam_.insert_cartridge(media.cartridges.front()->segments().front().data);
 
-		return !media.tapes.empty() || had_cartridge;
+		return !media.tapes.empty() || had_cartridge || (has_disk_drive && !media.disks.empty());
 	}
 
 	ChangeEffect effect_for_file_did_change(const std::string &) const override {
@@ -1042,6 +1047,9 @@ private:
 
 	void set_activity_observer(Activity::Observer *const observer) override {
 		tape_player_.set_activity_observer(observer);
+		if(has_disk_drive) {
+			disk_controller_.set_activity_observer(observer);
+		}
 	}
 
 	// MARK: - Joysticks.
@@ -1100,6 +1108,7 @@ private:
 	// MARK: - Disk.
 
 	DiskController disk_controller_;
+	Cycles cycles_16mhz_;
 };
 
 }
diff --git a/Machines/Tandy/CoCo/DiskController.cpp b/Machines/Tandy/CoCo/DiskController.cpp
index d0deec977..08ac739cc 100644
--- a/Machines/Tandy/CoCo/DiskController.cpp
+++ b/Machines/Tandy/CoCo/DiskController.cpp
@@ -11,10 +11,10 @@
 using namespace Tandy::CoCo;
 
 DiskController::DiskController() : WD::WD1770(P1773) {
-	emplace_drives(2, 8'000'000, 300, 2);
+	emplace_drives(4, 8'000'000, 300, 2);
 }
 
-void DiskController::set_control(uint8_t) {
+void DiskController::set_control(const uint8_t value) {
 	// TODO:
 	//
 	//	b7: halt flag, 1 = enabled
@@ -23,4 +23,33 @@ void DiskController::set_control(uint8_t) {
 	//	b4: write precompensation, 1 = enable
 	//	b3: drive motors, 1 = on
 	//	b0–b2: drive selects
+
+	set_is_double_density(value & 0x20);
+	for_all_drives([&] (Storage::Disk::Drive &drive, size_t) {
+		drive.set_motor_on(value & 0x8);
+	});
+	set_drive((value & 7) | ((value >> 3) & 8));
+
+	// TODO: HALT connection.
+}
+
+void DiskController::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, const size_t drive) {
+	get_drive(drive).set_disk(disk);
+}
+
+void DiskController::set_activity_observer(Activity::Observer *const observer) {
+	for_all_drives([observer] (Storage::Disk::Drive &drive, size_t index) {
+		drive.set_activity_observer(observer, "Drive " + std::to_string(index+1), true);
+	});
+}
+
+const Storage::Disk::Disk *DiskController::disk(const std::string &name) {
+	const Storage::Disk::Disk *result = nullptr;
+	for_all_drives( [&](Storage::Disk::Drive &drive, size_t) {
+		const auto disk = drive.disk();
+		if(disk && disk->represents(name)) {
+			result = disk;
+		}
+	});
+	return result;
 }
diff --git a/Machines/Tandy/CoCo/DiskController.hpp b/Machines/Tandy/CoCo/DiskController.hpp
index 615ad230c..423443c8c 100644
--- a/Machines/Tandy/CoCo/DiskController.hpp
+++ b/Machines/Tandy/CoCo/DiskController.hpp
@@ -9,6 +9,9 @@
 #pragma once
 
 #include "Components/1770/1770.hpp"
+#include "Activity/Observer.hpp"
+
+#include <string>
 
 namespace Tandy::CoCo {
 
@@ -35,6 +38,10 @@ public:
 			set_control(value);
 		}
 	}
+
+	void set_activity_observer(Activity::Observer *);
+	void set_disk(std::shared_ptr<Storage::Disk::Disk>, size_t drive);
+	const Storage::Disk::Disk *disk(const std::string &);
 };
 
 }