diff --git a/InstructionSets/6809/OperationMapper.hpp b/InstructionSets/6809/OperationMapper.hpp
index 002746706..99f35dfc1 100644
--- a/InstructionSets/6809/OperationMapper.hpp
+++ b/InstructionSets/6809/OperationMapper.hpp
@@ -309,7 +309,7 @@ auto OperationMapper<Page::Page0>::dispatch(SchedulerT &s) {
 				O::None,	O::DAA,		O::ORCC,	O::None,	O::ANDCC,	O::SEX,		O::EXG,		O::TFR,
 			};
 			static constexpr AddressingMode specific_modes[] = {
-				AM::Variant,	AM::Variant,	AM::Inherent,	AM::Inherent,
+				AM::Variant,	AM::Variant,	AM::Inherent,	AM::Specialised,
 				AM::Illegal,	AM::Illegal,	AM::Relative16,	AM::Relative16,
 				AM::Illegal,	AM::Inherent,	AM::Immediate8,	AM::Illegal,
 				AM::Immediate8,	AM::Inherent,	AM::Immediate8,	AM::Immediate8,
diff --git a/OSBindings/Mac/Clock SignalTests/6809Tests.mm b/OSBindings/Mac/Clock SignalTests/6809Tests.mm
index 11d59412f..0ccfd056c 100644
--- a/OSBindings/Mac/Clock SignalTests/6809Tests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/6809Tests.mm	
@@ -10,6 +10,7 @@
 #import <XCTest/XCTest.h>
 
 #include "Processors/6809/6809.hpp"
+#include "NSData+dataWithContentsOfGZippedFile.h"
 
 #include <unordered_map>
 
@@ -17,7 +18,7 @@ namespace {
 
 // This is a proto-single-step-tests file; I don't yet know the full veracity of its
 // source and it doesn't include bus activity.
-NSString *const testFile = @"/Users/thomasharte/Scratch/6809tests.json";
+NSString *const testFile = @"/Users/thomasharte/Scratch/6809tests.json.gz";
 
 struct M6809Capture {
 	std::unordered_map<uint16_t, uint8_t> ram;
@@ -32,14 +33,16 @@ struct M6809Capture {
 		const AddressT address,
 		CPU::M6809::data_t<read_write> value
 	) {
-		if constexpr (CPU::M6809::is_read(read_write)) {
-			const auto entry = ram.find(address);
-			if(entry == ram.end()) {
-				throw -1;
+		if constexpr (read_write != CPU::M6809::ReadWrite::NoData) {
+			if constexpr (CPU::M6809::is_read(read_write)) {
+				const auto entry = ram.find(address);
+				if(entry == ram.end()) {
+					throw -1;
+				}
+				value = entry->second;
+			} else {
+				ram[address] = value;
 			}
-			value = entry->second;
-		} else {
-			ram[address] = value;
 		}
 
 		return Cycles(0);
@@ -114,7 +117,8 @@ struct M6809Traits {
 
 		// Unimplemented by me.
 		case CWAI:
-		case SYNC: return;
+//		case SYNC:
+			return;
 
 		// Considered invalid by the test set.
 		case RESET: return;
@@ -257,7 +261,7 @@ struct M6809Traits {
 }
 
 - (void)testCaptures {
-	NSData *data = [NSData dataWithContentsOfFile:testFile];
+	NSData *data = [NSData dataWithContentsOfGZippedFile:testFile];
 	NSArray *tests = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
 
 	for(NSDictionary *test in tests) {
diff --git a/Processors/6809/6809.hpp b/Processors/6809/6809.hpp
index 0065f5937..478a14f45 100644
--- a/Processors/6809/6809.hpp
+++ b/Processors/6809/6809.hpp
@@ -314,6 +314,11 @@ struct Processor {
 				registers_.cc.set<ConditionCode::FIRQMask>(true);
 
 			reset_spin:
+			case ResumePoint::ResetSpin:
+				if(time_ <= 0) {
+					resume_point_ = ResumePoint::ResetSpin;
+					return;
+				}
 				if(exceptions_ & (Exception::Halt | Exception::DMABusReq | Exception::Reset)) {
 					inactive_bus();
 					goto reset_spin;
@@ -525,6 +530,9 @@ struct Processor {
 					case Operation::RESET:
 						goto swi_reset_nmi_irq;
 
+					case Operation::SYNC:
+						goto sync;
+
 					default: __builtin_unreachable();
 				}
 
@@ -765,6 +773,30 @@ struct Processor {
 				read(BusState::Normal, Literal(address_.full), registers_.pc.halves.low, ++address_.full);
 				goto fetch_decode;
 
+			sync:
+			case ResumePoint::Sync:
+				// Always consider taking a break here, regardless of selected pause precision; otherwise there's
+				// a risk of never exiting.
+				if(time_ <= 0) {
+					resume_point_ = ResumePoint::Sync;
+					return;
+				}
+
+				if(!(exceptions_ & (Exception::NMI | Exception::IRQ | Exception::FIRQ))) {
+					time_ -= Cycles(1);
+					time_ -=
+						bus_handler_.template perform<
+							BusPhase::FullCycle,
+							ReadWrite::NoData,
+							BusState::SyncAcknowledge
+						>(Address::Fixed<0xffff>(), Data::NoValue());
+
+					goto sync;
+				}
+
+				// TODO: understand the requirement that an interrupt be signalled for at least 3 cycles.
+
+				goto fetch_decode;
 
 			//
 			// Access atoms.
@@ -829,6 +861,8 @@ private:
 
 	enum ResumePoint {
 		FetchDecode,
+		ResetSpin,
+		Sync,
 		Max,
 	};
 	using Operation = InstructionSet::M6809::Operation;