diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperBase.cs b/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperBase.cs
new file mode 100644
index 0000000000..7b67757591
--- /dev/null
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperBase.cs
@@ -0,0 +1,36 @@
+using BizHawk.Common;
+using System;
+
+namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
+{
+	public class MapperBase
+	{
+		public A7800Hawk Core { get; set; }
+
+		public virtual byte ReadMemory(ushort addr)
+		{
+			return 0;
+		}
+
+		public virtual byte PeekMemory(ushort addr)
+		{
+			return 0;
+		}
+
+		public virtual void WriteMemory(ushort addr, byte value)
+		{
+		}
+
+		public virtual void PokeMemory(ushort addr, byte value)
+		{
+		}
+
+		public virtual void SyncState(Serializer ser)
+		{
+		}
+
+		public virtual void Dispose()
+		{
+		}
+	}
+}
diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperDefault.cs b/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperDefault.cs
new file mode 100644
index 0000000000..a92a98d8d3
--- /dev/null
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/A7800Hawk/Mappers/MapperDefault.cs
@@ -0,0 +1,100 @@
+using BizHawk.Common;
+using BizHawk.Common.NumberExtensions;
+using System;
+
+namespace BizHawk.Emulation.Cores.Atari.A7800Hawk
+{
+	// Default mapper with no bank switching
+	// Just need to keep track of high score bios stuff
+	public class MapperDefault : MapperBase
+	{
+		public override byte ReadMemory(ushort addr)
+		{
+			if (addr < 0x480)
+			{
+				// Nothing here
+				return 0xFF;
+			}
+			else if (addr < 0x1800)
+			{
+				//could be hsbios RAM here
+				if (addr >= 0x1000 && Core._hsbios != null)
+				{
+					return Core._hsram[addr - 0x1000];
+				}
+				return 0xFF;
+			}
+			else if (addr < 0x4000)
+			{
+				// could be either RAM mirror or ROM
+				if (addr >= 0x3000 && Core._hsbios != null)
+				{
+					return Core._hsbios[addr - 0x3000];
+				}
+				else
+				{
+					return Core.RAM[0x800 + addr & 0x7FF];
+				}
+			}
+			else
+			{
+				// cartridge and other OPSYS
+				if ((Core._rom.Length >= 0x10000 - addr) && Core.A7800_control_register.Bit(2))
+				{
+					return Core._rom[Core._rom.Length - (0x10000 - addr)];
+				}
+				else if (addr >= 0xF000 && !Core.A7800_control_register.Bit(2))
+				{
+					return Core._bios[addr - 0xF000];
+				}
+				else
+				{
+					return 0xFF;
+				}
+			}
+		}
+
+		public override byte PeekMemory(ushort addr)
+		{
+			return ReadMemory(addr);
+		}
+
+		public override void WriteMemory(ushort addr, byte value)
+		{
+			if (addr < 0x480)
+			{
+				// Nothing here
+			}
+			else if (addr < 0x1800)
+			{
+				//could be hsbios RAM here
+				if (addr >= 0x1000 && Core._hsbios != null)
+				{
+					Core._hsram[addr - 0x1000] = value;
+				}
+			}
+			else if (addr < 0x4000)
+			{
+				// could be either RAM mirror or ROM
+				if (addr >= 0x3000 && Core._hsbios != null)
+				{
+				}
+				else
+				{
+					Core.RAM[0x800 + addr & 0x7FF] = value;
+				}
+			}
+			else
+			{
+				// cartridge and other OPSYS
+			}
+		}
+
+		public override void PokeMemory(ushort addr, byte value)
+		{
+			WriteMemory(addr, value);
+		}
+
+
+	}
+}