diff --git a/src/agb/GBA.cpp b/src/agb/GBA.cpp
index 0fbb9a0b..06425f9a 100644
--- a/src/agb/GBA.cpp
+++ b/src/agb/GBA.cpp
@@ -2356,25 +2356,28 @@ void CPUCheckDMA(int reason, int dmamask)
 
 void CPUUpdateRegister(u32 address, u16 value)
 {
-  switch(address) {
+  switch(address)
+  {
   case 0x00:
-    {
-      if ((value & 7) >5)
-          DISPCNT = (value &7);
-      bool change = ((DISPCNT ^ value) & 0x80) ? true : false;
-      bool changeBG = ((DISPCNT ^ value) & 0x0F00) ? true : false;
-      u16 changeBGon = (((~DISPCNT) & value) & 0x0F00);
-      DISPCNT = (value & 0xFFF7);
+    { // we need to place the following code in { } because we declare & initialize variables in a case statement
+      if((value & 7) > 5) {
+        // display modes above 0-5 are prohibited
+        DISPCNT = (value & 7);
+      }
+      bool change = (0 != ((DISPCNT ^ value) & 0x80));
+      bool changeBG = (0 != ((DISPCNT ^ value) & 0x0F00));
+      u16 changeBGon = ((~DISPCNT) & value) & 0x0F00; // these layers are being activated
+
+      DISPCNT = (value & 0xFFF7); // bit 3 can only be accessed by the BIOS to enable GBC mode
       UPDATE_REG(0x00, DISPCNT);
 
-      if (changeBGon)
-      {
-         layerEnableDelay=4;
-         layerEnable = layerSettings & value & (~changeBGon);
+      if(changeBGon) {
+        layerEnableDelay = 4;
+        layerEnable = layerSettings & value & (~changeBGon);
+      } else {
+        layerEnable = layerSettings & value;
+        // CPUUpdateTicks();
       }
-       else
-         layerEnable = layerSettings & value;
-      //      CPUUpdateTicks();
 
       windowOn = (layerEnable & 0x6000) ? true : false;
       if(change && !((value & 0x80))) {
@@ -2390,10 +2393,11 @@ void CPUUpdateRegister(u32 address, u16 value)
       }
       CPUUpdateRender();
       // we only care about changes in BG0-BG3
-      if(changeBG)
+      if(changeBG) {
         CPUUpdateRenderBuffers(false);
+      }
+      break;
     }
-    break;
   case 0x04:
     DISPSTAT = (value & 0xFF38) | (DISPSTAT & 7);
     UPDATE_REG(0x04, DISPSTAT);
@@ -2739,9 +2743,9 @@ void CPUUpdateRegister(u32 address, u16 value)
       }
     }
     break;
- case 0x100:
+  case 0x100:
     timer0Reload = value;
-	interp_rate();
+    interp_rate();
     break;
   case 0x102:
     timer0Value = value;
@@ -2750,7 +2754,7 @@ void CPUUpdateRegister(u32 address, u16 value)
     break;
   case 0x104:
     timer1Reload = value;
-	interp_rate();
+    interp_rate();
     break;
   case 0x106:
     timer1Value = value;
@@ -2774,35 +2778,35 @@ void CPUUpdateRegister(u32 address, u16 value)
     cpuNextEvent = cpuTotalTicks;
     break;
   case 0x128:
-   #ifdef LINK_EMULATION
-	if (linkenable)
-	{
-		StartLink(value);
-	}
-	else
+#ifdef LINK_EMULATION
+    if (linkenable)
+    {
+      StartLink(value);
+    }
+    else
 #endif
-	{
-		if(value & 0x80) {
-		  value &= 0xff7f;
-		  if(value & 1 && (value & 0x4000)) {
-			UPDATE_REG(0x12a, 0xFF);
-			IF |= 0x80;
-			UPDATE_REG(0x202, IF);
-			value &= 0x7f7f;
-		  }
-		}
-	    UPDATE_REG(0x128, value);
-	}
+    {
+      if(value & 0x80) {
+        value &= 0xff7f;
+        if(value & 1 && (value & 0x4000)) {
+          UPDATE_REG(0x12a, 0xFF);
+          IF |= 0x80;
+          UPDATE_REG(0x202, IF);
+          value &= 0x7f7f;
+        }
+      }
+      UPDATE_REG(0x128, value);
+    }
+    break;
+  case 0x12a:
+#ifdef LINK_EMULATION
+    if(linkenable && lspeed)
+      LinkSSend(value);
+#endif
+    {
+      UPDATE_REG(0x134, value);
+    }
     break;
- case 0x12a:
- #ifdef LINK_EMULATION
- if(linkenable && lspeed)
-    LinkSSend(value);
-  #endif
-  {
- UPDATE_REG(0x134, value);
-  }
-  break;
   case 0x130:
     P1 |= (value & 0x3FF);
     UPDATE_REG(0x130, P1);
@@ -2812,22 +2816,22 @@ void CPUUpdateRegister(u32 address, u16 value)
     break;
   case 0x134:
 #ifdef LINK_EMULATION
-	if (linkenable)
-		StartGPLink(value);
-	else
+    if (linkenable)
+      StartGPLink(value);
+    else
 #endif
-	    UPDATE_REG(0x134, value);
+      UPDATE_REG(0x134, value);
 
-	break;
+    break;
   case 0x140:
 #ifdef LINK_EMULATION
-	if (linkenable)
-		StartJOYLink(value);
-	else
+    if (linkenable)
+      StartJOYLink(value);
+    else
 #endif
-	    UPDATE_REG(0x140, value);
+      UPDATE_REG(0x140, value);
 
-	break;
+    break;
   case 0x200:
     IE = value & 0x3FFF;
     UPDATE_REG(0x200, IE);
diff --git a/src/agb/GBAinline.h b/src/agb/GBAinline.h
index 833e3f30..53d75c6d 100644
--- a/src/agb/GBAinline.h
+++ b/src/agb/GBAinline.h
@@ -17,8 +17,8 @@
 // along with this program; if not, write to the Free Software Foundation,
 // Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
-#ifndef VBA_GBAinline_H
-#define VBA_GBAinline_H
+#ifndef GBAINLINE_H
+#define GBAINLINE_H
 
 #include "../System.h"
 #include "../Port.h"
@@ -67,7 +67,7 @@ static inline u32 CPUReadMemory(u32 address)
   if(address & 3) {
     if(systemVerbose & VERBOSE_UNALIGNED_MEMORY) {
       log("Unaligned word read: %08x at %08x\n", address, armMode ?
-          armNextPC - 4 : armNextPC - 2);
+        armNextPC - 4 : armNextPC - 2);
     }
   }
 #endif
@@ -80,7 +80,7 @@ static inline u32 CPUReadMemory(u32 address)
 #ifdef GBA_LOGGING
         if(systemVerbose & VERBOSE_ILLEGAL_READ) {
           log("Illegal word read: %08x at %08x\n", address, armMode ?
-              armNextPC - 4 : armNextPC - 2);
+            armNextPC - 4 : armNextPC - 2);
         }
 #endif
 
@@ -111,8 +111,8 @@ static inline u32 CPUReadMemory(u32 address)
     address = (address & 0x1fffc);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
     {
-        value = 0;
-        break;
+      value = 0;
+      break;
     }
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
@@ -139,11 +139,11 @@ static inline u32 CPUReadMemory(u32 address)
       return flashRead(address);
     // default
   default:
-  unreadable:
+unreadable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_READ) {
       log("Illegal word read: %08x at %08x\n", address, armMode ?
-          armNextPC - 4 : armNextPC - 2);
+        armNextPC - 4 : armNextPC - 2);
     }
 #endif
 
@@ -166,10 +166,10 @@ static inline u32 CPUReadMemory(u32 address)
 #else
 #ifdef __GNUC__
     asm("and $3, %%ecx;"
-        "shl $3 ,%%ecx;"
-        "ror %%cl, %0"
-        : "=r" (value)
-        : "r" (value), "c" (address));
+      "shl $3 ,%%ecx;"
+      "ror %%cl, %0"
+      : "=r" (value)
+      : "r" (value), "c" (address));
 #else
     __asm {
       mov ecx, address;
@@ -191,7 +191,7 @@ static inline u32 CPUReadHalfWord(u32 address)
   if(address & 1) {
     if(systemVerbose & VERBOSE_UNALIGNED_MEMORY) {
       log("Unaligned halfword read: %08x at %08x\n", address, armMode ?
-          armNextPC - 4 : armNextPC - 2);
+        armNextPC - 4 : armNextPC - 2);
     }
   }
 #endif
@@ -205,7 +205,7 @@ static inline u32 CPUReadHalfWord(u32 address)
 #ifdef GBA_LOGGING
         if(systemVerbose & VERBOSE_ILLEGAL_READ) {
           log("Illegal halfword read: %08x at %08x\n", address, armMode ?
-              armNextPC - 4 : armNextPC - 2);
+            armNextPC - 4 : armNextPC - 2);
         }
 #endif
         value = READ16LE(((u16 *)&biosProtected[address&2]));
@@ -228,14 +228,14 @@ static inline u32 CPUReadHalfWord(u32 address)
         if (((address & 0x3fe) == 0x100) && timer0On)
           value = 0xFFFF - ((timer0Ticks-cpuTotalTicks) >> timer0ClockReload);
         else
-        if (((address & 0x3fe) == 0x104) && timer1On && !(TM1CNT & 4))
-          value = 0xFFFF - ((timer1Ticks-cpuTotalTicks) >> timer1ClockReload);
-        else
-        if (((address & 0x3fe) == 0x108) && timer2On && !(TM2CNT & 4))
-          value = 0xFFFF - ((timer2Ticks-cpuTotalTicks) >> timer2ClockReload);
-        else
-        if (((address & 0x3fe) == 0x10C) && timer3On && !(TM3CNT & 4))
-          value = 0xFFFF - ((timer3Ticks-cpuTotalTicks) >> timer3ClockReload);
+          if (((address & 0x3fe) == 0x104) && timer1On && !(TM1CNT & 4))
+            value = 0xFFFF - ((timer1Ticks-cpuTotalTicks) >> timer1ClockReload);
+          else
+            if (((address & 0x3fe) == 0x108) && timer2On && !(TM2CNT & 4))
+              value = 0xFFFF - ((timer2Ticks-cpuTotalTicks) >> timer2ClockReload);
+            else
+              if (((address & 0x3fe) == 0x10C) && timer3On && !(TM3CNT & 4))
+                value = 0xFFFF - ((timer3Ticks-cpuTotalTicks) >> timer3ClockReload);
       }
     }
     else goto unreadable;
@@ -247,8 +247,8 @@ static inline u32 CPUReadHalfWord(u32 address)
     address = (address & 0x1fffe);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
     {
-        value = 0;
-        break;
+      value = 0;
+      break;
     }
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
@@ -278,11 +278,11 @@ static inline u32 CPUReadHalfWord(u32 address)
       return flashRead(address);
     // default
   default:
-  unreadable:
+unreadable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_READ) {
       log("Illegal halfword read: %08x at %08x\n", address, armMode ?
-          armNextPC - 4 : armNextPC - 2);
+        armNextPC - 4 : armNextPC - 2);
     }
 #endif
     if(cpuDmaHack) {
@@ -321,7 +321,7 @@ static inline u8 CPUReadByte(u32 address)
 #ifdef GBA_LOGGING
         if(systemVerbose & VERBOSE_ILLEGAL_READ) {
           log("Illegal byte read: %08x at %08x\n", address, armMode ?
-              armNextPC - 4 : armNextPC - 2);
+            armNextPC - 4 : armNextPC - 2);
         }
 #endif
         return biosProtected[address & 3];
@@ -341,7 +341,7 @@ static inline u8 CPUReadByte(u32 address)
   case 6:
     address = (address & 0x1ffff);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
-        return 0;
+      return 0;
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
     return vram[address];
@@ -362,23 +362,23 @@ static inline u8 CPUReadByte(u32 address)
       return flashRead(address);
     if(cpuEEPROMSensorEnabled) {
       switch(address & 0x00008f00) {
-      case 0x8200:
-        return systemGetSensorX() & 255;
-      case 0x8300:
-        return (systemGetSensorX() >> 8)|0x80;
-      case 0x8400:
-        return systemGetSensorY() & 255;
-      case 0x8500:
-        return systemGetSensorY() >> 8;
+  case 0x8200:
+    return systemGetSensorX() & 255;
+  case 0x8300:
+    return (systemGetSensorX() >> 8)|0x80;
+  case 0x8400:
+    return systemGetSensorY() & 255;
+  case 0x8500:
+    return systemGetSensorY() >> 8;
       }
     }
     // default
   default:
-  unreadable:
+unreadable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_READ) {
       log("Illegal byte read: %08x at %08x\n", address, armMode ?
-          armNextPC - 4 : armNextPC - 2);
+        armNextPC - 4 : armNextPC - 2);
     }
 #endif
     if(cpuDmaHack) {
@@ -401,9 +401,9 @@ static inline void CPUWriteMemory(u32 address, u32 value)
   if(address & 3) {
     if(systemVerbose & VERBOSE_UNALIGNED_MEMORY) {
       log("Unaligned word write: %08x to %08x from %08x\n",
-          value,
-          address,
-          armMode ? armNextPC - 4 : armNextPC - 2);
+        value,
+        address,
+        armMode ? armNextPC - 4 : armNextPC - 2);
     }
   }
 #endif
@@ -413,7 +413,7 @@ static inline void CPUWriteMemory(u32 address, u32 value)
 #ifdef BKPT_SUPPORT
     if(*((u32 *)&freezeWorkRAM[address & 0x3FFFC]))
       cheatsWriteMemory(address & 0x203FFFC,
-                        value);
+      value);
     else
 #endif
       WRITE32LE(((u32 *)&workRAM[address & 0x3FFFC]), value);
@@ -422,7 +422,7 @@ static inline void CPUWriteMemory(u32 address, u32 value)
 #ifdef BKPT_SUPPORT
     if(*((u32 *)&freezeInternalRAM[address & 0x7ffc]))
       cheatsWriteMemory(address & 0x3007FFC,
-                        value);
+      value);
     else
 #endif
       WRITE32LE(((u32 *)&internalRAM[address & 0x7ffC]), value);
@@ -437,15 +437,15 @@ static inline void CPUWriteMemory(u32 address, u32 value)
 #ifdef BKPT_SUPPORT
     if(*((u32 *)&freezePRAM[address & 0x3fc]))
       cheatsWriteMemory(address & 0x70003FC,
-                        value);
+      value);
     else
 #endif
-    WRITE32LE(((u32 *)&paletteRAM[address & 0x3FC]), value);
+      WRITE32LE(((u32 *)&paletteRAM[address & 0x3FC]), value);
     break;
   case 0x06:
     address = (address & 0x1fffc);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
-        return;
+      return;
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
 
@@ -455,16 +455,16 @@ static inline void CPUWriteMemory(u32 address, u32 value)
     else
 #endif
 
-    WRITE32LE(((u32 *)&vram[address]), value);
+      WRITE32LE(((u32 *)&vram[address]), value);
     break;
   case 0x07:
 #ifdef BKPT_SUPPORT
     if(*((u32 *)&freezeOAM[address & 0x3fc]))
       cheatsWriteMemory(address & 0x70003FC,
-                        value);
+      value);
     else
 #endif
-    WRITE32LE(((u32 *)&oam[address & 0x3fc]), value);
+      WRITE32LE(((u32 *)&oam[address & 0x3fc]), value);
     break;
   case 0x0D:
     if(cpuEEPROMEnabled) {
@@ -479,13 +479,13 @@ static inline void CPUWriteMemory(u32 address, u32 value)
     }
     // default
   default:
-  unwritable:
+unwritable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_WRITE) {
       log("Illegal word write: %08x to %08x from %08x\n",
-          value,
-          address,
-          armMode ? armNextPC - 4 : armNextPC - 2);
+        value,
+        address,
+        armMode ? armNextPC - 4 : armNextPC - 2);
     }
 #endif
     break;
@@ -498,9 +498,9 @@ static inline void CPUWriteHalfWord(u32 address, u16 value)
   if(address & 1) {
     if(systemVerbose & VERBOSE_UNALIGNED_MEMORY) {
       log("Unaligned halfword write: %04x to %08x from %08x\n",
-          value,
-          address,
-          armMode ? armNextPC - 4 : armNextPC - 2);
+        value,
+        address,
+        armMode ? armNextPC - 4 : armNextPC - 2);
     }
   }
 #endif
@@ -510,7 +510,7 @@ static inline void CPUWriteHalfWord(u32 address, u16 value)
 #ifdef BKPT_SUPPORT
     if(*((u16 *)&freezeWorkRAM[address & 0x3FFFE]))
       cheatsWriteHalfWord(address & 0x203FFFE,
-                          value);
+      value);
     else
 #endif
       WRITE16LE(((u16 *)&workRAM[address & 0x3FFFE]),value);
@@ -519,7 +519,7 @@ static inline void CPUWriteHalfWord(u32 address, u16 value)
 #ifdef BKPT_SUPPORT
     if(*((u16 *)&freezeInternalRAM[address & 0x7ffe]))
       cheatsWriteHalfWord(address & 0x3007ffe,
-                          value);
+      value);
     else
 #endif
       WRITE16LE(((u16 *)&internalRAM[address & 0x7ffe]), value);
@@ -533,33 +533,33 @@ static inline void CPUWriteHalfWord(u32 address, u16 value)
 #ifdef BKPT_SUPPORT
     if(*((u16 *)&freezePRAM[address & 0x03fe]))
       cheatsWriteHalfWord(address & 0x70003fe,
-                          value);
+      value);
     else
 #endif
-    WRITE16LE(((u16 *)&paletteRAM[address & 0x3fe]), value);
+      WRITE16LE(((u16 *)&paletteRAM[address & 0x3fe]), value);
     break;
   case 6:
     address = (address & 0x1fffe);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
-        return;
+      return;
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
 #ifdef BKPT_SUPPORT
     if(*((u16 *)&freezeVRAM[address]))
       cheatsWriteHalfWord(address + 0x06000000,
-                          value);
+      value);
     else
 #endif
-    WRITE16LE(((u16 *)&vram[address]), value);
+      WRITE16LE(((u16 *)&vram[address]), value);
     break;
   case 7:
 #ifdef BKPT_SUPPORT
     if(*((u16 *)&freezeOAM[address & 0x03fe]))
       cheatsWriteHalfWord(address & 0x70003fe,
-                          value);
+      value);
     else
 #endif
-    WRITE16LE(((u16 *)&oam[address & 0x3fe]), value);
+      WRITE16LE(((u16 *)&oam[address & 0x3fe]), value);
     break;
   case 8:
   case 9:
@@ -581,13 +581,13 @@ static inline void CPUWriteHalfWord(u32 address, u16 value)
     }
     goto unwritable;
   default:
-  unwritable:
+unwritable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_WRITE) {
       log("Illegal halfword write: %04x to %08x from %08x\n",
-          value,
-          address,
-          armMode ? armNextPC - 4 : armNextPC - 2);
+        value,
+        address,
+        armMode ? armNextPC - 4 : armNextPC - 2);
     }
 #endif
     break;
@@ -599,11 +599,11 @@ static inline void CPUWriteByte(u32 address, u8 b)
   switch(address >> 24) {
   case 2:
 #ifdef BKPT_SUPPORT
-      if(freezeWorkRAM[address & 0x3FFFF])
-        cheatsWriteByte(address & 0x203FFFF, b);
-      else
+    if(freezeWorkRAM[address & 0x3FFFF])
+      cheatsWriteByte(address & 0x203FFFF, b);
+    else
 #endif
-        workRAM[address & 0x3FFFF] = b;
+      workRAM[address & 0x3FFFF] = b;
     break;
   case 3:
 #ifdef BKPT_SUPPORT
@@ -616,13 +616,6 @@ static inline void CPUWriteByte(u32 address, u8 b)
   case 4:
     if(address < 0x4000400) {
       switch(address & 0x3FF) {
-      case 0x301:
-	if(b == 0x80)
-	  stopState = true;
-	holdState = 1;
-	holdType = -1;
-  cpuNextEvent = cpuTotalTicks;
-	break;
       case 0x60:
       case 0x61:
       case 0x62:
@@ -663,17 +656,22 @@ static inline void CPUWriteByte(u32 address, u8 b)
       case 0x9d:
       case 0x9e:
       case 0x9f:
-	soundEvent(address&0xFF, b);
-	break;
-      default:
-	if(address & 1)
-	  CPUUpdateRegister(address & 0x3fe,
-			    ((READ16LE(((u16 *)&ioMem[address & 0x3fe])))
-			     & 0x00FF) |
-			    b<<8);
-	else
-	  CPUUpdateRegister(address & 0x3fe,
-			    ((READ16LE(((u16 *)&ioMem[address & 0x3fe])) & 0xFF00) | b));
+        soundEvent(address&0xFF, b);
+        break;
+      case 0x301: // HALTCNT, undocumented
+        if(b == 0x80)
+          stopState = true;
+        holdState = 1;
+        holdType = -1;
+        cpuNextEvent = cpuTotalTicks;
+        break;
+      default: // every other register
+        u32 lowerBits = address & 0x3fe;
+        if(address & 1) {
+          CPUUpdateRegister(lowerBits, (READ16LE(&ioMem[lowerBits]) & 0x00FF) | (b << 8));
+        } else {
+          CPUUpdateRegister(lowerBits, (READ16LE(&ioMem[lowerBits]) & 0xFF00) | b);
+        }
       }
       break;
     } else goto unwritable;
@@ -685,7 +683,7 @@ static inline void CPUWriteByte(u32 address, u8 b)
   case 6:
     address = (address & 0x1fffe);
     if (((DISPCNT & 7) >2) && ((address & 0x1C000) == 0x18000))
-        return;
+      return;
     if ((address & 0x18000) == 0x18000)
       address &= 0x17fff;
 
@@ -698,7 +696,7 @@ static inline void CPUWriteByte(u32 address, u8 b)
         cheatsWriteByte(address + 0x06000000, b);
       else
 #endif
-            *((u16 *)&vram[address]) = (b << 8) | b;
+        *((u16 *)&vram[address]) = (b << 8) | b;
     }
     break;
   case 7:
@@ -713,26 +711,26 @@ static inline void CPUWriteByte(u32 address, u8 b)
     }
     goto unwritable;
   case 14:
-      if (!(saveType == 5) && (!eepromInUse | cpuSramEnabled | cpuFlashEnabled)) {
+    if (!(saveType == 5) && (!eepromInUse | cpuSramEnabled | cpuFlashEnabled)) {
 
-    //if(!cpuEEPROMEnabled && (cpuSramEnabled | cpuFlashEnabled)) {
+      //if(!cpuEEPROMEnabled && (cpuSramEnabled | cpuFlashEnabled)) {
 
-        (*cpuSaveGameFunc)(address, b);
+      (*cpuSaveGameFunc)(address, b);
       break;
     }
     // default
   default:
-  unwritable:
+unwritable:
 #ifdef GBA_LOGGING
     if(systemVerbose & VERBOSE_ILLEGAL_WRITE) {
       log("Illegal byte write: %02x to %08x from %08x\n",
-          b,
-          address,
-          armMode ? armNextPC - 4 : armNextPC -2 );
+        b,
+        address,
+        armMode ? armNextPC - 4 : armNextPC -2 );
     }
 #endif
     break;
   }
 }
 
-#endif //VBA_GBAinline_H
+#endif //GBAINLINE_H