diff --git a/snes-core/src/cpu/bus.rs b/snes-core/src/cpu/bus.rs
index 997cf3f..1870a0c 100644
--- a/snes-core/src/cpu/bus.rs
+++ b/snes-core/src/cpu/bus.rs
@@ -56,6 +56,22 @@ impl Bus {
         }
     }
 
+    /// This function is meant to be used by external parts of the code,
+    /// for example, to render register info without mutating them
+    pub fn read_external(&self, address: u32) -> u8 {
+        let section = Bus::map_address(address);
+        match section {
+            MemoryMap::WRAM => self.read_wram(address),
+            MemoryMap::PPU => self.ppu.registers.read_external(address as u16),
+            MemoryMap::CPU => self.internal_registers.read_external(
+                address as u16,
+                &self.ppu.registers,
+            ),
+            MemoryMap::Joypad => 0x00,  // TODO: Placeholder
+            MemoryMap::Cartridge => self.rom.read(address),
+        }
+    }
+
     pub fn read(&mut self, address: u32) -> u8 {
         let section = Bus::map_address(address);
         match section {
diff --git a/snes-core/src/cpu/internal_registers.rs b/snes-core/src/cpu/internal_registers.rs
index 48aec25..4178cb2 100644
--- a/snes-core/src/cpu/internal_registers.rs
+++ b/snes-core/src/cpu/internal_registers.rs
@@ -24,18 +24,31 @@ impl InternalRegisters {
         self.registers[(address - INTERNAL_REGISTERS_ADDRESS) as usize] = value
     }
 
-    pub fn read(&self, address: u16, ppu_registers: &mut PPURegisters) -> u8 {
+    pub fn read_external(&self, address: u16, ppu_registers: &PPURegisters) -> u8 {
         match address {
             RDNMI => self.read_vblank_nmi(ppu_registers),
             _ => self._read(address),
         }
     }
 
+    pub fn read(&self, address: u16, ppu_registers: &mut PPURegisters) -> u8 {
+        match address {
+            RDNMI => self.read_vblank_nmi_mut(ppu_registers),
+            _ => self._read(address),
+        }
+    }
+
     pub fn write(&mut self, address: u16, value: u8) {
         self._write(address, value);
     }
 
-    fn read_vblank_nmi(&self, ppu_registers: &mut PPURegisters) -> u8 {
+    fn read_vblank_nmi(&self, ppu_registers: &PPURegisters) -> u8 {
+        let byte = self._read(RDNMI);
+        let result = (byte & 0x7F) | ((ppu_registers.vblank_nmi as u8) << 7);
+        result
+    }
+
+    fn read_vblank_nmi_mut(&self, ppu_registers: &mut PPURegisters) -> u8 {
         let byte = self._read(RDNMI);
         // When register is read, bit 7 is cleared
         let result = (byte & 0x7F) | ((ppu_registers.vblank_nmi as u8) << 7);
diff --git a/snes-core/src/ppu/registers.rs b/snes-core/src/ppu/registers.rs
index 34d3b46..ced96ac 100644
--- a/snes-core/src/ppu/registers.rs
+++ b/snes-core/src/ppu/registers.rs
@@ -164,6 +164,10 @@ impl PPURegisters {
         self.data[(address as usize) - 0x2100] = value;
     }
 
+    pub fn read_external(&self, address: u16) -> u8 {
+        self._read(address)
+    }
+
     pub fn read(&mut self, address: u16) -> u8 {
         let result = self._read(address);
         match address {
diff --git a/snes-frontend/src/cpu.rs b/snes-frontend/src/cpu.rs
index 1138371..364711a 100644
--- a/snes-frontend/src/cpu.rs
+++ b/snes-frontend/src/cpu.rs
@@ -7,22 +7,21 @@ pub struct CPUDisassembler {
 }
 
 impl CPUDisassembler {
-    // TODO FIXME: please do not mutate the emulator state to fetch upcoming instructions
-    pub fn get_next_instruction(emulator: &mut Emulator) -> String {
-        let opcode = emulator.bus.read(emulator.cpu.registers.get_pc_address());
+    pub fn get_next_instruction(emulator: &Emulator) -> String {
+        let opcode = emulator.bus.read_external(emulator.cpu.registers.get_pc_address());
         let is_cpu_16bit = emulator.cpu.registers.is_16bit_mode();
         let is_index_16bit = emulator.cpu.registers.is_16bit_index();
-        let next_byte = emulator.bus.read(emulator.cpu.registers.get_pc_address() + 1);
-        let next_second_byte = emulator.bus.read(emulator.cpu.registers.get_pc_address() + 2);
-        let next_third_byte = emulator.bus.read(emulator.cpu.registers.get_pc_address() + 3);
+        let next_byte = emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 1);
+        let next_second_byte = emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 2);
+        let next_third_byte = emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 3);
         let next_word = {
-            (emulator.bus.read(emulator.cpu.registers.get_pc_address() + 1) as u16) |
-            ((emulator.bus.read(emulator.cpu.registers.get_pc_address() + 2) as u16) << 8)
+            (emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 1) as u16) |
+            ((emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 2) as u16) << 8)
         };
         let next_word_long = {
-            (emulator.bus.read(emulator.cpu.registers.get_pc_address() + 1) as u32) |
-            ((emulator.bus.read(emulator.cpu.registers.get_pc_address() + 2) as u32) << 8) |
-            ((emulator.bus.read(emulator.cpu.registers.get_pc_address() + 3) as u32) << 16)
+            (emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 1) as u32) |
+            ((emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 2) as u32) << 8) |
+            ((emulator.bus.read_external(emulator.cpu.registers.get_pc_address() + 3) as u32) << 16)
         };
         match opcode {
             // ADC
diff --git a/snes-frontend/src/main.rs b/snes-frontend/src/main.rs
index e4ab121..ea0ca82 100644
--- a/snes-frontend/src/main.rs
+++ b/snes-frontend/src/main.rs
@@ -404,7 +404,7 @@ fn main() {
                                         let mut address_row = format!("{:04X} | ", address);
                                         for page in (page_start..=page_end).rev() {
                                             let bus_address = ((page as u32) << 16) | (address as u32);
-                                            address_row = format!("{}{:02X} ", address_row, emulator.bus.read(bus_address));
+                                            address_row = format!("{}{:02X} ", address_row, emulator.bus.read_external(bus_address));
                                         }
                                         ui.text(address_row);
                                     }