diff --git a/libretro/libretro.cpp b/libretro/libretro.cpp
index b2383fd7..2e91fc38 100644
--- a/libretro/libretro.cpp
+++ b/libretro/libretro.cpp
@@ -328,19 +328,6 @@ void S9xAppendMapping(struct retro_memory_descriptor * desc)
 	memcpy(&memorydesc[64 - (++memorydesc_c)], desc, sizeof(struct retro_memory_descriptor));
 }
 
-//#define RETRO_MEMDESC_CONST (1 << 0)
-//struct retro_memory_descriptor {
-//   uint64_t flags;
-//   void * ptr;
-//   size_t offset;
-//   size_t start;
-//   size_t select;
-//   size_t disconnect;
-//   size_t len;
-//   const char * addrspace;
-//};
-//void S9xAppendMapping(struct retro_memory_descriptor desc);
-
 bool retro_load_game(const struct retro_game_info *game)
 {
    memorydesc_c = 0;
diff --git a/libretro/libretro.h b/libretro/libretro.h
index c62dcc94..e63aebb2 100755
--- a/libretro/libretro.h
+++ b/libretro/libretro.h
@@ -663,6 +663,7 @@ struct retro_memory_descriptor {
    //If the same byte is mapped my multiple descriptors, their descriptors must have the same pointer.
    //If 'start' does not point to the first byte in the pointer, put the difference in 'offset' instead.
    //May be NULL if there's nothing usable here (e.g. hardware registers and open bus). No flags should be set if the pointer is NULL.
+   //It's recommended to minimize the number of descriptors if possible, but not mandatory.
    void * ptr;
    size_t offset;
    
diff --git a/memmap.cpp b/memmap.cpp
index cdb2d4b8..3b0b8797 100644
--- a/memmap.cpp
+++ b/memmap.cpp
@@ -2787,7 +2787,7 @@ void CMemory::map_lorom (uint32 bank_s, uint32 bank_e, uint32 addr_s, uint32 add
 	desc.start=0;//
 	desc.select=0x8000;
 	desc.len=0;//
-	S9xAppendMapping(&desc);
+	//S9xAppendMapping(&desc);
 #endif
 }
 
@@ -2816,7 +2816,7 @@ void CMemory::map_hirom (uint32 bank_s, uint32 bank_e, uint32 addr_s, uint32 add
 	desc.select=0;//
 	desc.disconnect=0;
 	desc.len=0;//
-	S9xAppendMapping(&desc);
+	//S9xAppendMapping(&desc);
 #endif
 }
 
@@ -2845,7 +2845,7 @@ void CMemory::map_lorom_offset (uint32 bank_s, uint32 bank_e, uint32 addr_s, uin
 	desc.select=0;//
 	desc.disconnect=0x8000;
 	desc.len=0;//
-	S9xAppendMapping(&desc);
+	//S9xAppendMapping(&desc);
 #endif
 }
 
@@ -2873,7 +2873,7 @@ void CMemory::map_hirom_offset (uint32 bank_s, uint32 bank_e, uint32 addr_s, uin
 	desc.select=0;//
 	desc.disconnect=0x0000;
 	desc.len=0;//
-	S9xAppendMapping(&desc);
+	//S9xAppendMapping(&desc);
 #endif
 }
 
@@ -2896,11 +2896,11 @@ void CMemory::map_space (uint32 bank_s, uint32 bank_e, uint32 addr_s, uint32 add
 	desc.flags=0;
 	desc.ptr=data;
 	desc.offset=0;
-	if (data == RAM+0x10000) { desc.ptr=RAM; desc.offset=0x10000; }
-	desc.start=0;//
-	desc.select=0;//
-	desc.disconnect=0;//
-	desc.len=0;//
+	desc.start=bank_s<<16 | addr_s;
+	desc.select=(bank_s<<16 | addr_s) ^ (bank_e<<16 | addr_e) ^ 0xFFFFFF;
+	desc.disconnect=0;
+	desc.len=0;
+if (bank_s==0x7e || bank_s==0x7f)
 	S9xAppendMapping(&desc);
 #endif
 }
@@ -2975,7 +2975,7 @@ void CMemory::map_index (uint32 bank_s, uint32 bank_e, uint32 addr_s, uint32 add
 	desc.select=0;//
 	desc.disconnect=0;//
 	desc.len=0;//
-	S9xAppendMapping(&desc);
+	//S9xAppendMapping(&desc);
 #endif
 }
 
@@ -2993,8 +2993,8 @@ void CMemory::map_System (void)
 void CMemory::map_WRAM (void)
 {
 	// will overwrite others
-	map_space(0x7e, 0x7e, 0x0000, 0xffff, RAM);
 	map_space(0x7f, 0x7f, 0x0000, 0xffff, RAM + 0x10000);
+	map_space(0x7e, 0x7e, 0x0000, 0xffff, RAM);
 }
 
 void CMemory::map_LoROMSRAM (void)