From e9347168e61c071e04edfb397d050652ce0780cf Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 28 Jul 2023 10:53:02 -0400
Subject: [PATCH 1/3] Don't alter the data bank upon BRK, COP, IRQ, etc.

---
 Processors/65816/Implementation/65816Implementation.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Processors/65816/Implementation/65816Implementation.hpp b/Processors/65816/Implementation/65816Implementation.hpp
index bbb9dcedc..230d3723a 100644
--- a/Processors/65816/Implementation/65816Implementation.hpp
+++ b/Processors/65816/Implementation/65816Implementation.hpp
@@ -441,7 +441,9 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
 					if(registers_.emulation_flag) {
 						if(exception_is_interrupt_) data_buffer_.value &= ~uint32_t(Flag::Break);
 						data_buffer_.size = 3;
-						registers_.data_bank = 0;
+						if(pending_exceptions_ & (Reset | PowerOn)) {
+							registers_.data_bank = 0;
+						}
 						++next_op_;
 					} else {
 						data_buffer_.value |= registers_.program_bank << 8;	// The PBR is always held such that

From 0f1468adfd8581421f058ef847259a23a3daa7ab Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 28 Jul 2023 13:39:21 -0400
Subject: [PATCH 2/3] Correct wrapping behaviour for (d, x).

---
 .../Implementation/65816Implementation.hpp      | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/Processors/65816/Implementation/65816Implementation.hpp b/Processors/65816/Implementation/65816Implementation.hpp
index 230d3723a..c11705c1b 100644
--- a/Processors/65816/Implementation/65816Implementation.hpp
+++ b/Processors/65816/Implementation/65816Implementation.hpp
@@ -359,15 +359,20 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
 				continue;
 
 				case OperationConstructDirectIndexedIndirect:
-					data_address_ = (
-						((registers_.direct + registers_.x.full + instruction_buffer_.value) & registers_.e_masks[1]) +
-						(registers_.direct & registers_.e_masks[0])
-					) & 0xffff;
-					data_address_increment_mask_ = 0x00'ff'ff;
-
+					// Emulation mode plus DL = 0 is required for 6502-style functionality where
+					// only the low byte is the result of the indirect calculation.
 					if(!(registers_.direct&0xff)) {
+						data_address_ = (
+							((registers_.direct + registers_.x.full + instruction_buffer_.value) & registers_.e_masks[1]) +
+							(registers_.direct & registers_.e_masks[0])
+						) & 0xffff;
 						++next_op_;
+					} else {
+						data_address_ = (
+							registers_.direct + registers_.x.full + instruction_buffer_.value
+						) & 0xffff;
 					}
+					data_address_increment_mask_ = 0x00'ff'ff;
 				continue;
 
 				case OperationConstructDirectIndirectIndexedLong:

From 5d45aa4a6a6e8e820c0b1708aee9886ab6287475 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 28 Jul 2023 13:58:01 -0400
Subject: [PATCH 3/3] Fix seed per test.

---
 OSBindings/Mac/Clock SignalTests/65816ComparativeTests.mm | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/OSBindings/Mac/Clock SignalTests/65816ComparativeTests.mm b/OSBindings/Mac/Clock SignalTests/65816ComparativeTests.mm
index c342889a6..6017f35ac 100644
--- a/OSBindings/Mac/Clock SignalTests/65816ComparativeTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/65816ComparativeTests.mm	
@@ -155,14 +155,14 @@ void print_ram(FILE *file, const std::unordered_map<uint32_t, uint8_t> &data) {
 - (void)generate {
 	BusHandler handler;
 
-	// Make tests repeatable, at least for any given instance of
-	// the runtime.
-	srand(65816);
-
 	NSString *const tempDir = NSTemporaryDirectory();
 	NSLog(@"Outputting to %@", tempDir);
 
 	for(int operation = 0; operation < 512; operation++) {
+		// Make tests repeatable, at least for any given instance of
+		// the runtime.
+		srand(65816 + operation);
+
 		const bool is_emulated = operation & 256;
 		const uint8_t opcode = operation & 255;