diff --git a/lib/rubyboy/bus.rb b/lib/rubyboy/bus.rb
index c67b958..f0ad272 100644
--- a/lib/rubyboy/bus.rb
+++ b/lib/rubyboy/bus.rb
@@ -11,74 +11,93 @@ def initialize(ppu, rom, ram, mbc, timer, interrupt, joypad, apu)
       @apu = apu
       @interrupt = interrupt
       @timer = timer
+    end
+
+    def read_byte(addr)
+      case addr >> 12
+      when 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0xa, 0xb
+        return @mbc.read_byte(addr)
+      when 0x8, 0x9
+        return @ppu.read_byte(addr)
+      when 0xc
+        return @ram.wram1[addr - 0xc000]
+      when 0xd
+        return @ram.wram2[addr - 0xd000]
+      when 0xf
+        case addr >> 8
+        when 0xfe
+          return @ppu.read_byte(addr) if addr <= 0xfe9f
+        when 0xff
+          last_byte = addr & 0xFF
 
-      @read_methods = Array.new(0x10000)
-      @write_methods = Array.new(0x10000)
+          case last_byte
+          when 0x00
+            return @joypad.read_byte(addr)
+          when 0x04, 0x05, 0x06, 0x07
+            return @timer.read_byte(addr)
+          when 0x0f
+            return @interrupt.read_byte(addr)
+          when 0x46
+            return @ppu.read_byte(addr)
+          when 0xff
+            return @interrupt.read_byte(addr)
+          end
 
-      set_methods
-    end
+          return @apu.read_byte(addr) if last_byte <= 0x26 && last_byte >= 0x10
 
-    def set_methods
-      0x10000.times do |addr|
-        case addr
-        when 0x0000..0x7fff
-          @read_methods[addr] = -> { @mbc.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @mbc.write_byte(addr, value) }
-        when 0x8000..0x9fff
-          @read_methods[addr] = -> { @ppu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
-        when 0xa000..0xbfff
-          @read_methods[addr] = -> { @mbc.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @mbc.write_byte(addr, value) }
-        when 0xc000..0xcfff
-          @read_methods[addr] = -> { @ram.wram1[addr - 0xc000] }
-          @write_methods[addr] = ->(value) { @ram.wram1[addr - 0xc000] = value }
-        when 0xd000..0xdfff
-          @read_methods[addr] = -> { @ram.wram2[addr - 0xd000] }
-          @write_methods[addr] = ->(value) { @ram.wram2[addr - 0xd000] = value }
-        when 0xfe00..0xfe9f
-          @read_methods[addr] = -> { @ppu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
-        when 0xff00
-          @read_methods[addr] = -> { @joypad.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @joypad.write_byte(addr, value) }
-        when 0xff04..0xff07
-          @read_methods[addr] = -> { @timer.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @timer.write_byte(addr, value) }
-        when 0xff0f
-          @read_methods[addr] = -> { @interrupt.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @interrupt.write_byte(addr, value) }
-        when 0xff10..0xff26
-          @read_methods[addr] = -> { @apu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @apu.write_byte(addr, value) }
-        when 0xff30..0xff3f
-          @read_methods[addr] = -> { @apu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @apu.write_byte(addr, value) }
-        when 0xff46
-          @read_methods[addr] = -> { @ppu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { 0xa0.times { |i| write_byte(0xfe00 + i, read_byte((value << 8) + i)) } }
-        when 0xff40..0xff4b
-          @read_methods[addr] = -> { @ppu.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @ppu.write_byte(addr, value) }
-        when 0xff80..0xfffe
-          @read_methods[addr] = -> { @ram.hram[addr - 0xff80] }
-          @write_methods[addr] = ->(value) { @ram.hram[addr - 0xff80] = value }
-        when 0xffff
-          @read_methods[addr] = -> { @interrupt.read_byte(addr) }
-          @write_methods[addr] = ->(value) { @interrupt.write_byte(addr, value) }
-        else
-          @read_methods[addr] = -> { 0xff }
-          @write_methods[addr] = ->(_value) {}
+          return @apu.read_byte(addr) if last_byte <= 0x3f && last_byte >= 0x30
+
+          return @ppu.read_byte(addr) if last_byte <= 0x4b && last_byte >= 0x40
+
+          return @ram.hram[addr - 0xff80] if last_byte <= 0xfe && last_byte >= 0x80
         end
       end
-    end
 
-    def read_byte(addr)
-      @read_methods[addr].call
+      0xff
     end
 
     def write_byte(addr, value)
-      @write_methods[addr].call(value)
+      case addr >> 12
+      when 0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0xa, 0xb
+        return @mbc.write_byte(addr, value)
+      when 0x8, 0x9
+        return @ppu.write_byte(addr, value)
+      when 0xc
+        return @ram.wram1[addr - 0xc000] = value
+      when 0xd
+        return @ram.wram2[addr - 0xd000] = value
+      when 0xf
+        case addr >> 8
+        when 0xfe
+          return @ppu.write_byte(addr, value) if addr <= 0xfe9f
+        when 0xff
+          last_byte = addr & 0xFF
+
+          case last_byte
+          when 0x00
+            return @joypad.write_byte(addr, value)
+          when 0x04, 0x05, 0x06, 0x07
+            return @timer.write_byte(addr, value)
+          when 0x0f
+            return @interrupt.write_byte(addr, value)
+          when 0x46
+            0xa0.times { |i| write_byte(0xfe00 + i, read_byte((value << 8) + i)) }
+            return
+          when 0xff
+            return @interrupt.write_byte(addr, value)
+          end
+
+          return @apu.write_byte(addr, value) if last_byte <= 0x26 && last_byte >= 0x10
+
+          return @apu.write_byte(addr, value) if last_byte <= 0x3f && last_byte >= 0x30
+
+          return @ppu.write_byte(addr, value) if last_byte <= 0x4b && last_byte >= 0x40
+
+          return @ram.hram[addr - 0xff80] = value if last_byte <= 0xfe && last_byte >= 0x80
+        end
+      end
+
+      nil
     end
 
     def read_word(addr)