Fix usage of rom- and rambank selected to avoid modulo at every access

Co-authored-by: thatguy <>

pyboy/core/cartridge/base_mbc.py

@@ -123,7 +123,7 @@ def getitem(self, address):
         if 0x0000 <= address < 0x4000:
             return self.rombanks[0][address]
         elif 0x4000 <= address < 0x8000:
-            return self.rombanks[self.rombank_selected % self.external_rom_count][address - 0x4000]
+            return self.rombanks[self.rombank_selected][address - 0x4000]
         elif 0xA000 <= address < 0xC000:
             if not self.rambank_initialized:
                 logger.error("RAM banks not initialized: %s" % hex(address))
@@ -134,7 +134,7 @@ def getitem(self, address):
             if self.rtc_enabled and 0x08 <= self.rambank_selected <= 0x0C:
                 return self.rtc.getregister(self.rambank_selected)
             else:
-                return self.rambanks[self.rambank_selected % self.external_ram_count][address - 0xA000]
+                return self.rambanks[self.rambank_selected][address - 0xA000]
         else:
             logger.error("Reading address invalid: %s" % address)
 

pyboy/core/cartridge/mbc1.py

@@ -54,8 +54,8 @@ def getitem(self, address):
             return self.rombanks[self.rombank_selected][address]
         elif 0x4000 <= address < 0x8000:
             self.rombank_selected = \
-                    (self.bank_select_register2 << 5) % self.external_rom_count | self.bank_select_register1
-            return self.rombanks[self.rombank_selected % len(self.rombanks)][address - 0x4000]
+                    ((self.bank_select_register2 << 5) | self.bank_select_register1) % self.external_rom_count
+            return self.rombanks[self.rombank_selected][address - 0x4000]
         elif 0xA000 <= address < 0xC000:
             if not self.rambank_initialized:
                 logger.error("RAM banks not initialized: %s" % hex(address))
@@ -64,10 +64,10 @@ def getitem(self, address):
                 return 0xFF
 
             if self.memorymodel == 1:
-                self.rambank_selected = self.bank_select_register2
+                self.rambank_selected = self.bank_select_register2 % self.external_ram_count
             else:
                 self.rambank_selected = 0
-            return self.rambanks[self.rambank_selected % self.external_ram_count][address - 0xA000]
+            return self.rambanks[self.rambank_selected][address - 0xA000]
         else:
             logger.error("Reading address invalid: %s" % address)
 

pyboy/core/cartridge/mbc2.py

@@ -19,7 +19,7 @@ def setitem(self, address, value):
             else:
                 if value == 0:
                     value = 1
-                self.rombank_selected = value
+                self.rombank_selected = value % self.external_rom_count
         elif 0xA000 <= address < 0xC000:
             if self.rambanks is None:
                 logger.warning(
@@ -38,7 +38,7 @@ def getitem(self, address):
         if 0x0000 <= address < 0x4000:
             return self.rombanks[0][address]
         elif 0x4000 <= address < 0x8000:
-            return self.rombanks[self.rombank_selected % len(self.rombanks)][address - 0x4000]
+            return self.rombanks[self.rombank_selected][address - 0x4000]
         elif 0xA000 <= address < 0xC000:
             if not self.rambank_initialized:
                 logger.error("RAM banks not initialized: %s" % hex(address))

pyboy/core/cartridge/mbc3.py

@@ -27,9 +27,9 @@ def setitem(self, address, value):
             value &= 0b01111111
             if value == 0:
                 value = 1
-            self.rombank_selected = value
+            self.rombank_selected = value % self.external_rom_count
         elif 0x4000 <= address < 0x6000:
-            self.rambank_selected = value
+            self.rambank_selected = value % self.external_ram_count
         elif 0x6000 <= address < 0x8000:
             if self.rtc_enabled:
                 self.rtc.writecommand(value)

pyboy/core/cartridge/mbc5.py

@@ -17,12 +17,12 @@ def setitem(self, address, value):
             self.rambank_enabled = (value == 0b00001010)
         elif 0x2000 <= address < 0x3000:
             # 8-bit register used for the lower 8 bits of the ROM bank number.
-            self.rombank_selected = (self.rombank_selected & 0b100000000) | value
+            self.rombank_selected = ((self.rombank_selected & 0b100000000) | value) % self.external_rom_count
         elif 0x3000 <= address < 0x4000:
             # 1-bit register used for the most significant bit of the ROM bank number.
-            self.rombank_selected = ((value & 0x1) << 8) | (self.rombank_selected & 0xFF)
+            self.rombank_selected = (((value & 0x1) << 8) | (self.rombank_selected & 0xFF)) % self.external_rom_count
         elif 0x4000 <= address < 0x6000:
-            self.rambank_selected = value & 0xF
+            self.rambank_selected = (value & 0xF) % self.external_ram_count
         elif 0xA000 <= address < 0xC000:
             if self.rambanks is None:
                 logger.warning(
@@ -32,6 +32,6 @@ def setitem(self, address, value):
                 )
                 self.init_rambanks(self.external_ram_count)
             if self.rambank_enabled:
-                self.rambanks[self.rambank_selected % self.external_ram_count][address - 0xA000] = value
+                self.rambanks[self.rambank_selected][address - 0xA000] = value
         else:
             logger.debug("Unexpected write to 0x%0.4x, value: 0x%0.2x" % (address, value))