diff --git a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IDisassembler.cs b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IDisassembler.cs
index 3b47510b5a..473d033574 100644
--- a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IDisassembler.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IDisassembler.cs
@@ -29,9 +29,9 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx32
 
 		public string Disassemble(MemoryDomain m, uint addr, out int length)
 		{
-			_disassemblerInstance.ReadWord = (a) => (short)m.PeekWord(a, m.EndianType == MemoryDomain.Endian.Big);
+			_disassemblerInstance.ReadWord = (a) => (short)m.PeekUshort(a, m.EndianType == MemoryDomain.Endian.Big);
 			_disassemblerInstance.ReadByte = (a) => (sbyte)m.PeekByte(a);
-			_disassemblerInstance.ReadLong = (a) => (int)m.PeekDWord(a, m.EndianType == MemoryDomain.Endian.Big);
+			_disassemblerInstance.ReadLong = (a) => (int)m.PeekUint(a, m.EndianType == MemoryDomain.Endian.Big);
 			var info = _disassemblerInstance.Disassemble((int)addr);
 
 			length = info.Length;
diff --git a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IMemoryDomains.cs b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IMemoryDomains.cs
index 8794274b04..219d91abf1 100644
--- a/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IMemoryDomains.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Sega/gpgx32/GPGX.IMemoryDomains.cs
@@ -25,7 +25,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx32
 				{
 					// vram pokes need to go through hook which invalidates cached tiles
 					byte* p = (byte*)area;
-					mm.Add(new MemoryDomain(name, size, MemoryDomain.Endian.Unknown,
+					mm.Add(new MemoryDomainDelegate(name, size, MemoryDomain.Endian.Unknown,
 						delegate (long addr)
 						{
 							if (addr < 0 || addr >= 65536)
@@ -38,16 +38,18 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx32
 								throw new ArgumentOutOfRangeException();
 							LibGPGX.gpgx_poke_vram(((int)addr) ^ 1, val);
 						},
-						byteSize: 2));
+						wordSize: 2));
 				}
 
 				else
 				{
-					var byteSize = name.Contains("Z80") ? 1 : 2;
-					mm.Add(MemoryDomain.FromIntPtrSwap16(name, size, MemoryDomain.Endian.Big, area, writable: true, byteSize: byteSize));
+					// TODO: are the Z80 domains really Swap16 in the core?  Check this
+					//var byteSize = name.Contains("Z80") ? 1 : 2;
+					mm.Add(MemoryDomain.FromIntPtrSwap16(name, size,
+						MemoryDomain.Endian.Big, area, name != "MD CART" && name != "CD BOOT ROM"));
 				}
 			}
-			var m68Bus = new MemoryDomain("M68K BUS", 0x1000000, MemoryDomain.Endian.Big,
+			var m68Bus = new MemoryDomainDelegate("M68K BUS", 0x1000000, MemoryDomain.Endian.Big,
 				delegate (long addr)
 				{
 					var a = (uint)addr;
@@ -65,7 +67,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx32
 
 			mm.Add(m68Bus);
 
-			var s68Bus = new MemoryDomain("S68K BUS", 0x1000000, MemoryDomain.Endian.Big,
+			var s68Bus = new MemoryDomainDelegate("S68K BUS", 0x1000000, MemoryDomain.Endian.Big,
 				delegate (long addr)
 				{
 					var a = (uint)addr;
diff --git a/output/dll/libgenplusgx.dll b/output/dll/libgenplusgx.dll
index 1dcce9a51b..c5551edff9 100644
Binary files a/output/dll/libgenplusgx.dll and b/output/dll/libgenplusgx.dll differ