Propagate mode change.

InstructionSets/x86/Implementation/LoadStore.hpp

@@ -10,6 +10,7 @@
 
 #include "InstructionSets/x86/AccessType.hpp"
 #include "InstructionSets/x86/Descriptors.hpp"
+#include "InstructionSets/x86/Mode.hpp"
 
 #include <utility>
 
@@ -91,7 +92,14 @@ void lmsw(
 	read_t<uint16_t> source,
 	ContextT &context
 ) {
-	assert(false);
+	context.registers.set_msw(source);
+	if(source & 1) {
+		context.memory.set_mode(Mode::Protected286);
+		context.segments.set_mode(Mode::Protected286);
+	}
+
+	// TODO: all other bits. Anything?
+	assert(!(source & ~1));
 }
 
 template <DescriptorTable table, typename AddressT, typename InstructionT, typename ContextT>

InstructionSets/x86/Mode.hpp

@@ -0,0 +1,18 @@
+//
+//  Mode.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 22/03/2025.
+//  Copyright © 2025 Thomas Harte. All rights reserved.
+//
+
+#pragma once
+
+namespace InstructionSet::x86 {
+
+enum class Mode {
+	Real,
+	Protected286,
+};
+
+}

Machines/PCCompatible/Memory.hpp

@@ -14,6 +14,7 @@
 
 #include "Analyser/Static/PCCompatible/Target.hpp"
 #include "InstructionSets/x86/AccessType.hpp"
+#include "InstructionSets/x86/Mode.hpp"
 
 #include <array>
 
@@ -26,6 +27,7 @@ class Memory {
 
 public:
 	using AccessType = InstructionSet::x86::AccessType;
+	using Mode = InstructionSet::x86::Mode;
 
 	// Constructor.
 	Memory(Registers<x86_model> &registers, const Segments<x86_model> &segments) :
@@ -41,6 +43,10 @@ public:
 	void preauthorise_write([[maybe_unused]] InstructionSet::x86::Source segment, [[maybe_unused]] uint16_t start, [[maybe_unused]] uint32_t length) {}
 	void preauthorise_write([[maybe_unused]] uint32_t start, [[maybe_unused]] uint32_t length) {}
 
+	void set_mode(const Mode mode) {
+		mode_ = mode;
+	}
+
 	//
 	// Access call-ins.
 	//
@@ -183,6 +189,7 @@ private:
 	std::array<uint8_t, 1024*1024> memory{0xff};
 	Registers<x86_model> &registers_;
 	const Segments<x86_model> &segments_;
+	Mode mode_ = Mode::Real;
 
 	uint32_t address(const InstructionSet::x86::Source segment, const uint16_t offset) const {
 		return segments_.descriptors[segment].to_linear(offset) & 0xf'ffff;

Machines/PCCompatible/Registers.hpp

@@ -92,6 +92,9 @@ public:
 	}
 
 	uint16_t msw() const {	return machine_status_;	}
+	void set_msw(const uint16_t msw) {
+		machine_status_ = msw;
+	}
 
 	using DescriptorTable = InstructionSet::x86::DescriptorTable;
 	using DescriptorTableLocation = InstructionSet::x86::DescriptorTablePointer;

Machines/PCCompatible/Segments.hpp

@@ -11,6 +11,7 @@
 #include "Registers.hpp"
 
 #include "InstructionSets/x86/Instruction.hpp"
+#include "InstructionSets/x86/Mode.hpp"
 #include "InstructionSets/x86/Model.hpp"
 
 namespace PCCompatible {
@@ -20,18 +21,24 @@ class Segments {
 public:
 	Segments(const Registers<model> &registers) : registers_(registers) {}
 
-	using Source = InstructionSet::x86::Source;
-	using DescriptorTable = InstructionSet::x86::DescriptorTable;
 	using Descriptor = InstructionSet::x86::Descriptor;
+	using DescriptorTable = InstructionSet::x86::DescriptorTable;
+	using Mode = InstructionSet::x86::Mode;
+	using Source = InstructionSet::x86::Source;
 
 	/// Posted by @c perform after any operation which *might* have affected a segment register.
 	void did_update(const Source segment) {
 		if(!is_segment_register(segment)) return;
+		assert(mode_ == Mode::Real);
 		descriptors[segment].set_segment(registers_.segment(segment));
 	}
 
 	void did_update(DescriptorTable) {}
 
+	void set_mode(const Mode mode) {
+		mode_ = mode;
+	}
+
 	void reset() {
 		did_update(Source::ES);
 		did_update(Source::CS);
@@ -46,6 +53,7 @@ public:
 	}
 
 private:
+	Mode mode_ = Mode::Real;
 	const Registers<model> &registers_;
 };
 

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -1760,6 +1760,7 @@
 		4B85322922778E4200F26553 /* Comparative68000.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Comparative68000.hpp; sourceTree = "<group>"; };
 		4B85322E2277ABDD00F26553 /* tos100.trace.txt.gz */ = {isa = PBXFileReference; lastKnownFileType = archive.gzip; path = tos100.trace.txt.gz; sourceTree = "<group>"; };
 		4B8671EA2D8B40D8009E1610 /* Descriptors.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Descriptors.hpp; sourceTree = "<group>"; };
+		4B8671EB2D8FABA0009E1610 /* Mode.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = Mode.hpp; sourceTree = "<group>"; };
 		4B86E2591F8C628F006FAA45 /* Keyboard.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Keyboard.cpp; sourceTree = "<group>"; };
 		4B86E25A1F8C628F006FAA45 /* Keyboard.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Keyboard.hpp; sourceTree = "<group>"; };
 		4B8805EE1DCFC99C003085B1 /* Acorn.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Acorn.cpp; path = Parsers/Acorn.cpp; sourceTree = "<group>"; };
@@ -5368,6 +5369,7 @@
 				42437B342ACF02A9006DFED1 /* Flags.hpp */,
 				4BEDA3DB25B2588F000C2DBD /* Instruction.hpp */,
 				42437B392AD07465006DFED1 /* Interrupts.hpp */,
+				4B8671EB2D8FABA0009E1610 /* Mode.hpp */,
 				4BE3C69527CBC540000EAD28 /* Model.hpp */,
 				42437B352ACF0AA2006DFED1 /* Perform.hpp */,
 				42437B372ACF2798006DFED1 /* Implementation */,