Add Bios INT 12h to report installed memory size. (#562)

* Add Bios INT 12h to report installed memory size.

* Update to clarify that INT12 only reports on the first 640k conventional memory

src/Spice86.Core/Emulator/InterruptHandlers/Bios/SystemBiosInt12Handler.cs

@@ -0,0 +1,31 @@
+namespace Spice86.Core.Emulator.InterruptHandlers.Bios;
+
+using Spice86.Core.Emulator.CPU;
+using Spice86.Core.Emulator.Memory;
+using Spice86.Shared.Interfaces;
+
+/// <summary>
+/// INT 12h handler. Reports how many kb of base memory is installed.
+/// </summary>
+public class SystemBiosInt12Handler : InterruptHandler {
+ private readonly BiosDataArea _biosDataArea;
+
+ /// <summary>
+ /// Initializes a new instance.
+ /// </summary>
+ /// <param name="memory"></param>
+ /// <param name="cpu"></param>
+ /// <param name="biosDataArea"></param>
+ /// <param name="loggerService"></param>
+ public SystemBiosInt12Handler(IMemory memory, Cpu cpu, BiosDataArea biosDataArea, ILoggerService loggerService) : base(memory, cpu, loggerService) {
+ _biosDataArea = biosDataArea;
+ }
+
+ /// <inheritdoc />
+ public override byte VectorNumber => 0x12;
+
+ /// <inheritdoc />
+ public override void Run() {
+ _state.AX = _biosDataArea.ConventionalMemorySizeKb;
+ }
+}

src/Spice86.Core/Emulator/Memory/BiosDataArea.cs

@@ -40,7 +40,10 @@ public BiosDataArea(IByteReaderWriter byteReaderWriter) : base(byteReaderWriter,
 
  // Padding at 0x12
 
- public ushort MemSizeKb { get => UInt16[0x13]; set => UInt16[0x13] = value; }
+ /// <summary>
+ /// Gets or sets the amount of installed conventional memory in KB.
+ /// </summary>
+ public ushort ConventionalMemorySizeKb { get => UInt16[0x13]; init => UInt16[0x13] = value; }
 
  // Padding at 0x15
 

src/Spice86.Core/Emulator/VM/Machine.cs

@@ -129,6 +129,11 @@ public sealed class Machine : IDisposable, IDebuggableComponent {
  /// </summary>
  public SoundBlaster SoundBlaster { get; }
 
+ /// <summary>
+ /// INT12H handler.
+ /// </summary>
+ public SystemBiosInt12Handler SystemBiosInt12Handler { get; }
+
  /// <summary>
  /// INT15H handler.
  /// </summary>
@@ -200,7 +205,9 @@ public Machine(IGui? gui, State cpuState, IOPortDispatcher ioPortDispatcher, ILo
  Memory.UInt16[0xF000, 0xFFF0] = 0xF4;
  }
  IoPortDispatcher = ioPortDispatcher;
- BiosDataArea = new BiosDataArea(Memory);
+ BiosDataArea = new BiosDataArea(Memory) {
+ ConventionalMemorySizeKb = (ushort)Math.Clamp(Memory.Ram.Size / 1024, 0, 640) // max 640k conventional memory
+ };
  CpuState = cpuState;
  DualPic = new(CpuState, configuration.FailOnUnhandledPort, configuration.InitializeDOS is false, loggerService);
  // Breakpoints
@@ -265,6 +272,7 @@ public Machine(IGui? gui, State cpuState, IOPortDispatcher ioPortDispatcher, ILo
  BiosKeyboardInt9Handler = new BiosKeyboardInt9Handler(Memory, Cpu, DualPic, Keyboard, BiosDataArea, loggerService);
 
  BiosEquipmentDeterminationInt11Handler = new BiosEquipmentDeterminationInt11Handler(Memory, Cpu, loggerService);
+ SystemBiosInt12Handler = new SystemBiosInt12Handler(Memory, Cpu, BiosDataArea, loggerService);
  SystemBiosInt15Handler = new SystemBiosInt15Handler(Memory, Cpu, Memory.A20Gate, loggerService);
  KeyboardInt16Handler = new KeyboardInt16Handler(Memory, Cpu, loggerService, BiosKeyboardInt9Handler.BiosKeyboardBuffer);
 
@@ -279,6 +287,7 @@ public Machine(IGui? gui, State cpuState, IOPortDispatcher ioPortDispatcher, ILo
  RegisterInterruptHandler(TimerInt8Handler);
  RegisterInterruptHandler(BiosKeyboardInt9Handler);
  RegisterInterruptHandler(BiosEquipmentDeterminationInt11Handler);
+ RegisterInterruptHandler(SystemBiosInt12Handler);
  RegisterInterruptHandler(SystemBiosInt15Handler);
  RegisterInterruptHandler(KeyboardInt16Handler);
  RegisterInterruptHandler(SystemClockInt1AHandler);