diff --git a/zsnes/src/init.asm b/zsnes/src/init.asm
index f9caaa7f..7955a696 100644
--- a/zsnes/src/init.asm
+++ b/zsnes/src/init.asm
@@ -95,7 +95,7 @@ EXTSYM GUIfindUSA,GUIfindEUR,GUIfindJAP,GUIfindZIP,GUIfind1,DTALoc,GUIfindall
 EXTSYM spc7110romptr,allocspc7110
 EXTSYM SRAMDir,SRAMDrive,cfgloadsdir,fnamest,statefileloc
 EXTSYM ForcePal,ForceROMTiming,ForceHiLoROM,InitDir,InitDrive,enterpress,frameskip
-EXTSYM infoloc
+EXTSYM maxromspace,curromspace,infoloc
 EXTSYM gotoroot,headdata,printnum,romispal
 EXTSYM InitFxTables,SFXSRAM,SfxR1,SfxR2,SfxSCMR,SfxSFR,finterleave
 EXTSYM initregr,initregw,memtabler16,DSP1Read16b3F,memaccessbankr16
@@ -2452,39 +2452,13 @@ NEWSYM initsnes
     mov dword[NoiseDisTemp+4],0
     mov byte[MMXSRAMFix],0
 
+    ;Megaman/Rockman X
     mov esi,[romdata]
     add esi,7FC0h
-    cmp dword[esi],'MEGA'
-    jne .notmmx
     cmp dword[esi+4],'MAN '
     jne .notmmx
     cmp dword[esi+8],'X   '
     jne .notmmx
-    mov esi,[romdata]
-    cmp byte[esi+824Ah],0F0h
-    jne .mmxa
-    mov byte[esi+824Ah],080h
-.mmxa
-    cmp byte[esi+21FC3h],0F0h
-    jne .mmxb
-    mov byte[esi+21FC3h],080h
-.mmxb
-    cmp byte[esi+2241Bh],0F0h
-    jne .mmxc
-    mov byte[esi+2241Bh],080h
-.mmxc
-    cmp byte[esi+824Fh],0F0h
-    jne .mmxd
-    mov byte[esi+824Fh],080h
-.mmxd
-    cmp byte[esi+21FC8h],0F0h
-    jne .mmxe
-    mov byte[esi+21FC8h],080h
-.mmxe
-    cmp byte[esi+22420h],0F0h
-    jne .mmxf
-    mov byte[esi+22420h],080h
-.mmxf
     mov byte[MMXSRAMFix],1
 .notmmx
 
@@ -4713,7 +4687,7 @@ NEWSYM loadfileGUI
     mov dword[.curfileofs],0
     mov byte[.first],1
     mov byte[.multfound],0
-    mov dword[.curromspace],0
+    mov dword[curromspace],0
     ; open file
     mov edx,fname+1
     call Open_File
@@ -4745,8 +4719,8 @@ NEWSYM loadfileGUI
     je .no16mb
     sub ecx,2097152
 .no16mb
-    mov [.maxromspace],ecx
-    sub dword[.maxromspace],32768
+    mov [maxromspace],ecx
+    sub dword[maxromspace],32768
     sub ecx,[.curfileofs]
     jnc .nooverflow
     xor ecx,ecx
@@ -4758,7 +4732,7 @@ NEWSYM loadfileGUI
 
     or eax,eax
     jz near .success2
-    add dword[.curromspace],eax
+    add dword[curromspace],eax
     mov esi,[headdata]
     add esi,[.curfileofs]
     mov edi,[headdata]
@@ -4793,7 +4767,7 @@ NEWSYM loadfileGUI
     add edi,512
     sub eax,512
     ; move eax # of bytes from edi to esi
-    sub dword[.curromspace],512
+    sub dword[curromspace],512
     sub dword[.curfileofs],512
 .next
     mov cl,[edi]
@@ -5047,8 +5021,6 @@ SECTION .bss
 .filehand resw 1
 .temp resb 1
 .fail resb 1
-.maxromspace resd 1
-.curromspace resd 1
 NEWSYM GUIloadfailed, resb 1
 
 SECTION .text
@@ -5913,7 +5885,14 @@ NEWSYM CheckROMType
     call GenerateBank0Table
 
     EXTSYM BankCheck
+    pushad
     call BankCheck
+    popad    
+
+    EXTSYM MirrorROM
+    pushad
+    call MirrorROM
+    popad    
 
     ; Chip Detection
     mov byte[SFXEnable],0
@@ -6394,3 +6373,4 @@ SECTION .text
 
 NEWSYM InitAsmEnd
 
+
diff --git a/zsnes/src/initc.c b/zsnes/src/initc.c
index 303b8009..e0cf7823 100755
--- a/zsnes/src/initc.c
+++ b/zsnes/src/initc.c
@@ -26,6 +26,9 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 #define Hi 0xFFC0
 #define EHi 0x40FFC0
 
+#define MB_bytes 0x100000
+#define Mbit_bytes 0x20000
+
 
 //I want to port over the more complicated
 //functions from init.asm, or replace with
@@ -41,8 +44,8 @@ extern unsigned char Interleaved;
 
 
 
-
-
+unsigned int maxromspace;
+unsigned int curromspace;
 unsigned int infoloc;
 
 //Deinterleave functions
@@ -231,13 +234,13 @@ void BankCheck()
     }
     switch(ROM[Hi + 21])
     {
-      case 33: case 49: case 53:
+      case 33: case 49: case 53: case 58:
       case 128: case 156: case 176: case 188: case 252: //BS
         hiscore += 1;      
         break;
     }
     
-    if(ForceHiLoROM)
+    if (ForceHiLoROM)
     {
       //asm volatile("int $3");
       if (forceromtype == 1) { loscore += 50; }
@@ -265,7 +268,7 @@ unsigned short sum(unsigned char *array, unsigned int size)
   unsigned int i;
   
   //Prevent crashing by reading too far (needed for messed up ROMs)
-  if (array + size > (unsigned char *)romdata + NumofBytes)
+  if (array + size > (unsigned char *)romdata + maxromspace)
   {
     return(0xFFFF);
   } 
@@ -283,33 +286,52 @@ extern unsigned short Checksumvalue;
 void CalcChecksum()
 {
   unsigned char *ROM = (unsigned char *)romdata;
-  unsigned short Mbit = NumofBanks >> 2;
-  
-  if ((Mbit == 10 || Mbit == 20 || Mbit == 40) && !SPC7110Enable)
-  {
-    unsigned int P1Size = 512 << ROM[infoloc + 23];
-    unsigned short part1 = sum(ROM, P1Size),
-                   part2 = sum(ROM+P1Size, NumofBytes-P1Size);
-    Checksumvalue = part1 + part2*4;
-  }
-  else if ((Mbit == 12 || Mbit == 24 || Mbit == 48) && !SPC7110Enable)
-  {
-    unsigned int P1Size = 512 << ROM[infoloc + 23];
-    unsigned short part1 = sum(ROM, P1Size),
-                   part2 = sum(ROM+P1Size, NumofBytes-P1Size);
-    Checksumvalue = part1 + part2 + part2;
-  }
-  else
+  if (SPC7110Enable)
   {
     Checksumvalue = sum(ROM, NumofBytes);
-    if (BSEnable)
-    {
-      Checksumvalue -= sum(&ROM[infoloc - 16], 48); //Fix for BS Dumps
-    }
-    else if (Mbit == 24)
+    if (NumofBanks == 96)
     { 
       Checksumvalue += Checksumvalue; //Fix for 24Mb SPC7110 ROMs
     }
   }
+  else
+  {
+    Checksumvalue = sum(ROM, curromspace);
+    if (NumofBanks > 128 && maxromspace == 6*MB_bytes)
+    { 
+      Checksumvalue += sum(ROM+4*MB_bytes, 2*MB_bytes);
+    }
+    if (BSEnable)
+    {
+      Checksumvalue -= sum(&ROM[infoloc - 16], 48); //Fix for BS Dumps
+    }
+  }
 }
 
+//Misc functions
+void MirrorROM()
+{
+  unsigned char *ROM = (unsigned char *)romdata;
+  int size, StartMirror = 0, ROMSize = curromspace;
+  //This will mirror up non power of two ROMs to powers of two
+  for (size = 1; size <= 64; size +=size)
+  {
+    int fullSize = size * Mbit_bytes,
+        halfSize = fullSize >> 1;
+    if ((ROMSize > halfSize) && (ROMSize < fullSize))
+    {
+      for (StartMirror = halfSize;
+           ROMSize < fullSize && ROMSize < maxromspace;)
+      {
+        ROM[ROMSize++] = ROM[StartMirror++];
+      }
+      curromspace = ROMSize;
+      break;
+    }
+  }
+  //This will mirror (now) full sized ROMs through the ROM buffer
+  for (StartMirror = 0; ROMSize < maxromspace;)
+  {
+    ROM[ROMSize++] = ROM[StartMirror++];
+  }
+}