diff --git a/src/BizHawk.Emulation.Cores/CPUs/LR35902/Execute.cs b/src/BizHawk.Emulation.Cores/CPUs/LR35902/Execute.cs
index 2d26819a9d..5d22c0adec 100644
--- a/src/BizHawk.Emulation.Cores/CPUs/LR35902/Execute.cs
+++ b/src/BizHawk.Emulation.Cores/CPUs/LR35902/Execute.cs
@@ -573,7 +573,7 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 			instr_table[256 * 60 * 2 + 10] = HALT_CHK;
 			instr_table[256 * 60 * 2 + 11] = OP;
 
-			// halt loop
+			// exit halt / stop loop
 			instr_table[256 * 60 * 2 + 60] = IDLE;
 			instr_table[256 * 60 * 2 + 60 + 1] = IDLE;
 			instr_table[256 * 60 * 2 + 60 + 2] = IDLE;
diff --git a/src/BizHawk.Emulation.Cores/CPUs/LR35902/LR35902.cs b/src/BizHawk.Emulation.Cores/CPUs/LR35902/LR35902.cs
index 53dcf5125f..a2f9e90cc4 100644
--- a/src/BizHawk.Emulation.Cores/CPUs/LR35902/LR35902.cs
+++ b/src/BizHawk.Emulation.Cores/CPUs/LR35902/LR35902.cs
@@ -377,7 +377,7 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 							}
 							else
 							{
-								instr_pntr = 256 * 60 * 2 + 60; // point to halt loop
+								instr_pntr = 256 * 60 * 2 + 60; // exit halt loop
 							}
 						}
 						else
@@ -444,10 +444,9 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 							});
 
 							stopped = false;
-							OnExecFetch?.Invoke(RegPC);
-							if (TraceCallback != null && !CB_prefix) TraceCallback(State());
-							CDLCallback?.Invoke(RegPC, eCDLogMemFlags.FetchFirst);
-							FetchInstruction(ReadMemory(RegPC++));
+
+							// it takes the CPU 4 cycles longer to restart then the rest of the system.
+							instr_pntr = 256 * 60 * 2 + 60;
 
 							stop_check = false;
 						}
@@ -458,7 +457,7 @@ namespace BizHawk.Emulation.Cores.Components.LR35902
 					}
 					else if (interrupt_src_reg.Bit(4)) // button pressed, even if interrupts are not enabled, still exists stop
 					{
-						// TODO: OnExecFetch a gameboy, you can only un-STOP once, needs further testing
+						// TODO: On a gameboy, you can only un-STOP once, needs further testing
 						
 						TraceCallback?.Invoke(new TraceInfo
 						{
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_GB_PPU.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_GB_PPU.cs
index cfb9ea5858..f0560de210 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_GB_PPU.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_GB_PPU.cs
@@ -27,10 +27,13 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public int HDMA_tick;
 		public byte HDMA_byte;
 
-		// accessors for derived values
-		public byte BG_pal_ret => (byte)(((BG_bytes_inc ? 1 : 0) << 7) | (BG_bytes_index & 0x3F));
+		// the first read on GBA (and first two on GBC) encounter access glitches if the source address is VRAM
+		public byte HDMA_VRAM_access_glitch;
 
-		public byte OBJ_pal_ret => (byte)(((OBJ_bytes_inc ? 1 : 0) << 7) | (OBJ_bytes_index & 0x3F));
+		// accessors for derived values
+		public byte BG_pal_ret => (byte)(((BG_bytes_inc ? 1 : 0) << 7) | (BG_bytes_index & 0x3F) | 0x40);
+
+		public byte OBJ_pal_ret => (byte)(((OBJ_bytes_inc ? 1 : 0) << 7) | (OBJ_bytes_index & 0x3F) | 0x40);
 
 		public byte HDMA_ctrl => (byte)(((HDMA_active ? 0 : 1) << 7) | ((HDMA_length >> 4) - 1));
 
@@ -71,10 +74,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF4B: ret = window_x;						break; // WX
 
 				// These are GBC specific Regs
-				case 0xFF51: ret = HDMA_src_hi;						break; // HDMA1
-				case 0xFF52: ret = HDMA_src_lo;						break; // HDMA2
-				case 0xFF53: ret = HDMA_dest_hi;					break; // HDMA3
-				case 0xFF54: ret = HDMA_dest_lo;					break; // HDMA4
+				case 0xFF51: ret = 0xFF;							break; // HDMA1 (src_hi)
+				case 0xFF52: ret = 0xFF;							break; // HDMA2 (src_lo)
+				case 0xFF53: ret = 0xFF;							break; // HDMA3 (dest_hi)
+				case 0xFF54: ret = 0xFF;							break; // HDMA4 (dest_lo)
 				case 0xFF55: ret = HDMA_ctrl;						break; // HDMA5
 				case 0xFF68: ret = BG_pal_ret;						break; // BGPI
 				case 0xFF69: ret = BG_PAL_read();					break; // BGPD
@@ -110,6 +113,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 						OAM_access_write = true;
 
 						clear_screen = true;
+
+						// turing off the screen causes HDMA to run for one cycle
+						HDMA_run_once = true;
 					}
 
 					if (!LCDC.Bit(7) && value.Bit(7))
@@ -184,6 +190,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF51: // HDMA1
 					HDMA_src_hi = value;
 					cur_DMA_src = (ushort)(((HDMA_src_hi & 0xFF) << 8) | (cur_DMA_src & 0xF0));
+					// similar to normal DMA, except HDMA transfers when A14 is high always access SRAM
+					if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
 					break;
 				case 0xFF52: // HDMA2
 					HDMA_src_lo = value;
@@ -215,19 +223,29 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							HBL_test = true;
 							HBL_HDMA_go = false;
 
-							if (!LCDC.Bit(7))
-							{
-								HDMA_run_once = true;
-							}
+							if (!LCDC.Bit(7)) { HDMA_run_once = true; }
+							else { HDMA_run_once = false; }
 						}
 						else
 						{
 							// HDMA immediately
 							HDMA_active = true;
 							Core.HDMA_transfer = true;
+							VRAM_access_read = false;
 						}
+						//Console.WriteLine(cur_DMA_src + " " + cur_DMA_dest + " " + Core.cpu.TotalExecutedCycles);
 
 						HDMA_length = ((value & 0x7F) + 1) * 16;
+
+						if (!LCDC.Bit(7))
+						{
+							// NOTE: GBA SP apparently only has one glitched access, not sure what gameboy player is
+							HDMA_VRAM_access_glitch = 2;
+						}
+						else
+						{
+							HDMA_VRAM_access_glitch = 0;
+						}
 					}
 					else
 					{
@@ -235,7 +253,11 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 						if (!value.Bit(7))
 						{
 							HDMA_active = false;
+							Core.HDMA_transfer = false;
 						}
+
+						// always update length
+						HDMA_length = ((value & 0x7F) + 1) * 16;
 					}
 
 					break;
@@ -288,13 +310,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							// immediately transfer bytes, 2 bytes per cycles
 							if ((HDMA_tick % 2) == 0)
 							{
-								HDMA_byte = Core.ReadMemory(cur_DMA_src);
+								if (HDMA_VRAM_access_glitch > 0)
+								{
+									HDMA_byte = Core.ReadMemory(Core.cpu.RegPC);
+									HDMA_VRAM_access_glitch--;
+								}
+								else
+								{
+									HDMA_byte = Core.ReadMemory(cur_DMA_src);
+								}
 							}
 							else
 							{
 								Core.VRAM[(Core.VRAM_Bank * 0x2000) + cur_DMA_dest] = HDMA_byte;
 								cur_DMA_dest = (ushort)((cur_DMA_dest + 1) & 0x1FFF);
 								cur_DMA_src = (ushort)((cur_DMA_src + 1) & 0xFFFF);
+
+								// similar to normal DMA, except HDMA transfers when A14 is high always access SRAM
+								if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
+
 								HDMA_length--;
 							}
 
@@ -304,16 +338,19 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					else
 					{
 						// only transfer during mode 0, and only 16 bytes at a time
-						if (((STAT & 3) == 0) && (LY != last_HBL) && HBL_test && (LY_inc == 1) && (cycle > 4))
+						// cycle > 90 prevents triggering early when turning on LCD (presumably the real event is transition from mode 3 to 0.)
+						if (((STAT & 3) == 0) && (LY != last_HBL) && HBL_test && (LY_inc == 1) && (cycle > 90))
 						{
 							HBL_HDMA_go = true;
 							HBL_test = false;
+							VRAM_access_read = false;
 						}
 						else if (HDMA_run_once)
 						{
 							HBL_HDMA_go = true;
 							HBL_test = false;
 							HDMA_run_once = false;
+							VRAM_access_read = false;
 						}
 
 						if (HBL_HDMA_go && (HBL_HDMA_count > 0))
@@ -328,13 +365,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							{
 								if ((HDMA_tick % 2) == 0)
 								{
-									HDMA_byte = Core.ReadMemory(cur_DMA_src);
+									if (HDMA_VRAM_access_glitch > 0)
+									{
+										HDMA_byte = Core.ReadMemory(Core.cpu.RegPC);
+										HDMA_VRAM_access_glitch--;
+									}
+									else
+									{
+										HDMA_byte = Core.ReadMemory(cur_DMA_src);
+									}
 								}
 								else
 								{
 									Core.VRAM[(Core.VRAM_Bank * 0x2000) + cur_DMA_dest] = HDMA_byte;
 									cur_DMA_dest = (ushort)((cur_DMA_dest + 1) & 0x1FFF);
 									cur_DMA_src = (ushort)((cur_DMA_src + 1) & 0xFFFF);
+
+									// similar to normal DMA, except HDMA transfers when A14 is high always access SRAM
+									if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
+
 									HDMA_length--;
 									HBL_HDMA_count--;
 								}
@@ -343,7 +392,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 								{
 
 									HBL_test = true;
-									last_HBL = LY;
+									if (LCDC.Bit(7)) { last_HBL = LY; }
+									else { last_HBL = 0xFF; }
 									HBL_HDMA_count = 0x10;
 									HBL_HDMA_go = false;
 									HDMA_countdown = 4;
@@ -355,6 +405,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 						else
 						{
 							Core.HDMA_transfer = false;
+							VRAM_access_read = true;
 						}
 					}
 				}
@@ -362,6 +413,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				{
 					HDMA_active = false;
 					Core.HDMA_transfer = false;
+					VRAM_access_read = true;
 				}
 			}
 
@@ -1611,6 +1663,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			ser.Sync(nameof(HDMA_dest_lo), ref HDMA_dest_lo);
 			ser.Sync(nameof(HDMA_tick), ref HDMA_tick);
 			ser.Sync(nameof(HDMA_byte), ref HDMA_byte);
+			ser.Sync(nameof(HDMA_VRAM_access_glitch), ref HDMA_VRAM_access_glitch);
 
 			ser.Sync(nameof(VRAM_sel), ref VRAM_sel);
 			ser.Sync(nameof(BG_V_flip), ref BG_V_flip);
@@ -1703,6 +1756,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			last_HBL = 0;
 			HBL_HDMA_go = false;
 			HBL_test = false;
+			HDMA_VRAM_access_glitch = 0;
+
+			for (int i = 0; i < BG_bytes.Length; i++) { BG_bytes[i] = 0xFF; }
+			for (int i = 0; i < OBJ_bytes.Length; i++) { OBJ_bytes[i] = 0xFF; }
 		}
 
 		public override void Reg_Copy(GBC_PPU ppu2)
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_PPU.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_PPU.cs
index 98c53b2b7a..7379416e7b 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_PPU.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBC_PPU.cs
@@ -25,10 +25,13 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 		public int HDMA_tick;
 		public byte HDMA_byte;
 
-		// accessors for derived values
-		public byte BG_pal_ret => (byte)(((BG_bytes_inc ? 1 : 0) << 7) | (BG_bytes_index & 0x3F));
+		// the first read on GBA (and first two on GBC) encounter access glitches if the source address is VRAM
+		public byte HDMA_VRAM_access_glitch;
 
-		public byte OBJ_pal_ret => (byte)(((OBJ_bytes_inc ? 1 : 0) << 7) | (OBJ_bytes_index & 0x3F));
+		// accessors for derived values
+		public byte BG_pal_ret => (byte)(((BG_bytes_inc ? 1 : 0) << 7) | (BG_bytes_index & 0x3F) | 0x40);
+
+		public byte OBJ_pal_ret => (byte)(((OBJ_bytes_inc ? 1 : 0) << 7) | (OBJ_bytes_index & 0x3F) | 0x40);
 
 		public byte HDMA_ctrl => (byte)(((HDMA_active ? 0 : 1) << 7) | ((HDMA_length >> 4) - 1));
 
@@ -69,10 +72,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF4B: ret = window_x;						break; // WX
 
 				// These are GBC specific Regs
-				case 0xFF51: ret = HDMA_src_hi;						break; // HDMA1
-				case 0xFF52: ret = HDMA_src_lo;						break; // HDMA2
-				case 0xFF53: ret = HDMA_dest_hi;					break; // HDMA3
-				case 0xFF54: ret = HDMA_dest_lo;					break; // HDMA4
+				case 0xFF51: ret = 0xFF;							break; // HDMA1 (src_hi)
+				case 0xFF52: ret = 0xFF;							break; // HDMA2 (src_lo)
+				case 0xFF53: ret = 0xFF;							break; // HDMA3 (dest_hi)
+				case 0xFF54: ret = 0xFF;							break; // HDMA4 (dest_lo)
 				case 0xFF55: ret = HDMA_ctrl;						break; // HDMA5
 				case 0xFF68: ret = BG_pal_ret;						break; // BGPI
 				case 0xFF69: ret = BG_PAL_read();					break; // BGPD
@@ -106,6 +109,9 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 						VRAM_access_write = true;
 						OAM_access_read = true;
 						OAM_access_write = true;
+
+						// turing off the screen causes HDMA to run for one cycle
+						HDMA_run_once = true;
 					}
 
 					if (!LCDC.Bit(7) && value.Bit(7))
@@ -180,6 +186,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF51: // HDMA1
 					HDMA_src_hi = value;
 					cur_DMA_src = (ushort)(((HDMA_src_hi & 0xFF) << 8) | (cur_DMA_src & 0xF0));
+					if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
 					break;
 				case 0xFF52: // HDMA2
 					HDMA_src_lo = value;
@@ -211,27 +218,40 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							HBL_test = true;
 							HBL_HDMA_go = false;
 
-							if (!LCDC.Bit(7))
-							{
-								HDMA_run_once =true;
-							}
+							if (!LCDC.Bit(7)) { HDMA_run_once = true; }
+							else { HDMA_run_once = false; }
 						}
 						else
 						{
 							// HDMA immediately
 							HDMA_active = true;
 							Core.HDMA_transfer = true;
+							VRAM_access_read = false;
 						}
+						//Console.WriteLine(cur_DMA_src + " " + cur_DMA_dest + " " + Core.cpu.TotalExecutedCycles);
 
 						HDMA_length = ((value & 0x7F) + 1) * 16;
+
+						if (!LCDC.Bit(7) && (cur_DMA_src >= 0x8000) && (cur_DMA_src < 0xA000))
+						{
+							// NOTE: GBA SP apparently only has one glitched access, not sure what gameboy player is
+							HDMA_VRAM_access_glitch = 2;
+						}
+						else
+						{
+							HDMA_VRAM_access_glitch = 0;
+						}
 					}
 					else
 					{
-						//terminate the transfer
+						//terminate the transfer if disabling
 						if (!value.Bit(7))
 						{
 							HDMA_active = false;
+							Core.HDMA_transfer = false;
 						}
+						// always update length
+						HDMA_length = ((value & 0x7F) + 1) * 16;
 					}
 
 					break;
@@ -284,13 +304,23 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							// immediately transfer bytes, 2 bytes per cycles
 							if ((HDMA_tick % 2) == 0)
 							{
-								HDMA_byte = Core.ReadMemory(cur_DMA_src);
+								if (HDMA_VRAM_access_glitch > 0)
+								{
+									HDMA_byte = Core.ReadMemory(Core.cpu.RegPC);
+									HDMA_VRAM_access_glitch--;
+								}
+								else
+								{
+									HDMA_byte = Core.ReadMemory(cur_DMA_src);
+								}
 							}
 							else
 							{
 								Core.VRAM[(Core.VRAM_Bank * 0x2000) + cur_DMA_dest] = HDMA_byte;
 								cur_DMA_dest = (ushort)((cur_DMA_dest + 1) & 0x1FFF);
 								cur_DMA_src = (ushort)((cur_DMA_src + 1) & 0xFFFF);
+								if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
+
 								HDMA_length--;
 							}
 
@@ -300,16 +330,19 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					else
 					{
 						// only transfer during mode 0, and only 16 bytes at a time
-						if (((STAT & 3) == 0) && (LY != last_HBL) && HBL_test && (LY_inc == 1) && (cycle > 4))
+						// cycle > 90 prevents triggering early when turning on LCD (presumably the real event is transition from mode 3 to 0.)
+						if (((STAT & 3) == 0) && (LY != last_HBL) && HBL_test && (LY_inc == 1) && (cycle > 90))
 						{
 							HBL_HDMA_go = true;
 							HBL_test = false;
+							VRAM_access_read = false;
 						}
 						else if (HDMA_run_once)
 						{
 							HBL_HDMA_go = true;
 							HBL_test = false;
 							HDMA_run_once = false;
+							VRAM_access_read = false;
 						}
 
 						if (HBL_HDMA_go && (HBL_HDMA_count > 0))
@@ -324,13 +357,23 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 							{
 								if ((HDMA_tick % 2) == 0)
 								{
-									HDMA_byte = Core.ReadMemory(cur_DMA_src);
+									if (HDMA_VRAM_access_glitch > 0)
+									{
+										HDMA_byte = Core.ReadMemory(Core.cpu.RegPC);
+										HDMA_VRAM_access_glitch--;
+									}
+									else
+									{
+										HDMA_byte = Core.ReadMemory(cur_DMA_src);
+									}
 								}
 								else
 								{
 									Core.VRAM[(Core.VRAM_Bank * 0x2000) + cur_DMA_dest] = HDMA_byte;
 									cur_DMA_dest = (ushort)((cur_DMA_dest + 1) & 0x1FFF);
 									cur_DMA_src = (ushort)((cur_DMA_src + 1) & 0xFFFF);
+									if (cur_DMA_src >= 0xE000) { cur_DMA_src &= 0xBFFF; }
+
 									HDMA_length--;
 									HBL_HDMA_count--;
 								}
@@ -339,7 +382,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 								{
 
 									HBL_test = true;
-									last_HBL = LY;
+									if (LCDC.Bit(7)) { last_HBL = LY; }
+									else { last_HBL = 0xFF; }
 									HBL_HDMA_count = 0x10;
 									HBL_HDMA_go = false;
 									HDMA_countdown = 4;
@@ -351,6 +395,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 						else
 						{
 							Core.HDMA_transfer = false;
+							VRAM_access_read = true;
 						}
 					}					
 				}
@@ -358,6 +403,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				{
 					HDMA_active = false;
 					Core.HDMA_transfer = false;
+					VRAM_access_read = true;
 				}
 			}		
 			
@@ -1557,6 +1603,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			ser.Sync(nameof(HDMA_dest_lo), ref HDMA_dest_lo);
 			ser.Sync(nameof(HDMA_tick), ref HDMA_tick);
 			ser.Sync(nameof(HDMA_byte), ref HDMA_byte);
+			ser.Sync(nameof(HDMA_VRAM_access_glitch), ref HDMA_VRAM_access_glitch);
 
 			ser.Sync(nameof(VRAM_sel), ref VRAM_sel);
 			ser.Sync(nameof(BG_V_flip), ref BG_V_flip);
@@ -1651,6 +1698,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			last_HBL = 0;
 			HBL_HDMA_go = false;
 			HBL_test = false;
+			HDMA_VRAM_access_glitch = 0;
+
+			for (int i = 0; i < BG_bytes.Length; i++) { BG_bytes[i] = 0xFF; }
+			for (int i = 0; i < OBJ_bytes.Length; i++) { OBJ_bytes[i] = 0xFF; }
 		}
 	}
 }
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.IEmulator.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.IEmulator.cs
index 5a766e8ff0..bc10211eff 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.IEmulator.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.IEmulator.cs
@@ -117,11 +117,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				else
 				{
 					cpu.TotalExecutedCycles++;
-					timer.tick();				
+					timer.tick();
+
 					if (double_speed)
 					{
 						cpu.TotalExecutedCycles++;
-						timer.tick();				
+						timer.tick();
 					}
 				}
 
@@ -259,7 +260,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				{
 					speed_switch = false;
 					Console.WriteLine("Speed Switch: " + cpu.TotalExecutedCycles);
-					int ret = double_speed ? (32768 - 19) : (32768 - 19); // actual time needs checking
+					int ret = double_speed ? (32768 - 20) : (32768 - 20); // actual time needs checking
 					double_speed = !double_speed;
 					return ret;
 				}
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/HW_Registers.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/HW_Registers.cs
index 5f59a4db60..bda2d6e028 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/HW_Registers.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/HW_Registers.cs
@@ -110,7 +110,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					break;
 
 				case 0xFF4F: // VBK
-					if (GBC_compat)
+					if (is_GBC)
 					{
 						ret = (byte)(0xFE | VRAM_Bank);
 					}
@@ -164,7 +164,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF69:
 				case 0xFF6A:
 				case 0xFF6B:
-					if (GBC_compat)
+					if (is_GBC)
 					{
 						ret = ppu.ReadReg(addr);
 					}
@@ -176,7 +176,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 
 				// Ram bank for GBC
 				case 0xFF70:
-					if (is_GBC)
+					if (GBC_compat)
 					{
 						ret = (byte)RAM_Bank;
 					}
@@ -393,7 +393,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 
 				// VBK
 				case 0xFF4F:
-					if (GBC_compat && !ppu.HDMA_active)
+					if (is_GBC/* && !ppu.HDMA_active*/)
 					{
 						VRAM_Bank = (byte)(value & 1);
 					}
@@ -439,15 +439,15 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 				case 0xFF69:
 				case 0xFF6A:
 				case 0xFF6B:
-					//if (GBC_compat)
-					//{
+					if (is_GBC)
+					{
 						ppu.WriteReg(addr, value);
-					//}
+					}
 					break;
 
 				// RAM Bank in GBC mode
 				case 0xFF70:
-					if (is_GBC)
+					if (GBC_compat)
 					{
 						RAM_Bank = value & 7;
 						if (RAM_Bank == 0) { RAM_Bank = 1; }
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/MemoryMap.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/MemoryMap.cs
index cd4a5141cb..99513d1ce5 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/MemoryMap.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/MemoryMap.cs
@@ -135,11 +135,19 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 					return VRAM[VRAM_Bank * 0x2000 + (addr - 0x8000)];
 				}
 
-				if (ppu.pixel_counter == 160) 
+				if (!HDMA_transfer)
 				{
-					return ppu.bus_return; 
+					if (ppu.pixel_counter == 160)
+					{
+						return ppu.bus_return;
+					}
+
+					return 0xFF;
 				}
-				return 0xFF;
+				else
+				{
+					return 0xFF;
+				}				
 			}
 
 			if (addr < 0xC000)
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Timer.cs b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Timer.cs
index 163c2c5cb0..ce4d96d33e 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Timer.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/Timer.cs
@@ -1,4 +1,5 @@
-using BizHawk.Common;
+using System;
+using BizHawk.Common;
 using BizHawk.Common.NumberExtensions;
 
 namespace BizHawk.Emulation.Cores.Nintendo.GBHawk