diff --git a/src/emu/i8088.rs b/src/emu/i8088.rs
index 41e6c3f..d2c84d6 100644
--- a/src/emu/i8088.rs
+++ b/src/emu/i8088.rs
@@ -130,80 +130,164 @@ impl<'a> RValue<u8> for RegHi<'a> {
   }
 }
 
+struct RegLo<'a> {
+  reg: &'a mut u16
+}
+
+impl<'a> LValue<u8> for RegLo<'a> {
+  fn write(&mut self, val: u8) {
+    write_lo(&mut self.reg, val);
+  }
+}
+
+impl<'a> RValue<u8> for RegLo<'a> {
+  fn read(&self) -> u8 {
+    read_lo(*self.reg)
+  }
+}
+
 macro_rules! step {
   // Base case: all args processed and ready to call op
   (@code ( $($args:tt)* ),
-         $cpu:expr, $bus:expr, $name:ident, $cycles:literal,
+         $cpu:expr, $bus:expr, $modrm:ident, $name:ident, $cycles:literal,
          ()) => {
     ops::$name($($args),*);
   };
 
   // Inductive case: decode next arg to be placed in list
   (@code ( $($args:tt)* ),
-         $cpu:expr, $bus:expr, $name:ident, $cycles:literal,
+         $cpu:expr, $bus:expr, $modrm:ident, $name:ident, $cycles:literal,
          ($next:ident $(= $nextrhs:ident)? $($rest:ident $(= $restrhs:ident)?)*)) => {
     step!(@$next$(= $nextrhs)?
-          ( ($($args)*), $cpu, $bus, $name, $cycles, ($($rest $(= $restrhs)?)*) ),
-          $cpu, $bus)
+          ( ($($args)*), $cpu, $bus, $modrm, $name, $cycles, ($($rest $(= $restrhs)?)*) ),
+          $cpu, $bus, $modrm)
   };
 
   // accept an argument from a decoder and recur to look for next arg
-  (@arg ( ($($args:tt)*), $cpu:expr, $bus:expr, $name:ident, $cycles:literal, ( $($rest:tt)* ) ),
+  (@arg ( ($($args:tt)*), $cpu:expr, $bus:expr, $modrm:ident, $name:ident, $cycles:literal, ( $($rest:tt)* ) ),
         $arg:expr) => {
-    step!(@code ($($args)* $arg), $cpu, $bus, $name, $cycles, ( $($rest)* ))
+    step!(@code ($($args)* $arg), $cpu, $bus, $modrm, $name, $cycles, ( $($rest)* ))
   };
 
   // Argument Decoders
 
-  (@bus $cookie:tt, $cpu:expr, $bus:expr) => { {
+  (@bus $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
     step!(@arg $cookie, $bus)
   } };
 
-  (@cpu $cookie:tt, $cpu:expr, $bus:expr) => { {
+  (@cpu $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
     step!(@arg $cookie, $cpu)
   } };
 
-  (@d8 $cookie:tt, $cpu:expr, $bus:expr) => { {
+  (@d8 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
     let d8 = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
     step!(@arg $cookie, &d8)
   } };
 
-  (@d16 $cookie:tt, $cpu:expr, $bus:expr) => { {
+  (@d16 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
     let mut buf = [0; 2];
     buf[0] = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
     buf[1] = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
     step!(@arg $cookie, &LittleEndian::read_u16(&buf))
   } };
 
-  (@mem $cookie:tt, $cpu:expr, $bus:expr) => {
+  (@mem $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => {
     step!(@arg $cookie, &mut $bus.ram)
   };
 
-  (@reg=$reg:ident $cookie:tt, $cpu:expr, $bus:expr) => {
+  (@modrm16 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
+    unimplemented!("step!(@arg $cookie, &mut ...)")
+  } };
+
+  (@r16 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
+    let reg = match $modrm >> 3 & 0x7 {
+      0 => &mut $cpu.a,
+      1 => &mut $cpu.c,
+      2 => &mut $cpu.d,
+      3 => &mut $cpu.b,
+      4 => &mut $cpu.sp,
+      5 => &mut $cpu.bp,
+      6 => &mut $cpu.si,
+      7 => &mut $cpu.di,
+      _ => unreachable!()
+    };
+    step!(@arg $cookie, reg)
+  } };
+
+  (@r8 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => {
+    match $modrm >> 3 & 0x7 {
+      0 => step!(@arg $cookie, &mut RegHi { reg: &mut $cpu.a } ),
+      1 => step!(@arg $cookie, &mut RegHi { reg: &mut $cpu.c } ),
+      2 => step!(@arg $cookie, &mut RegHi { reg: &mut $cpu.d } ) ,
+      3 => step!(@arg $cookie, &mut RegHi { reg: &mut $cpu.b } ),
+      4 => step!(@arg $cookie, &mut RegLo { reg: &mut $cpu.a } ),
+      5 => step!(@arg $cookie, &mut RegLo { reg: &mut $cpu.c } ),
+      6 => step!(@arg $cookie, &mut RegLo { reg: &mut $cpu.d } ),
+      7 => step!(@arg $cookie, &mut RegLo { reg: &mut $cpu.b } ),
+      _ => unreachable!()
+    };
+  };
+
+  (@reg=$reg:ident $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => {
     step!(@arg $cookie, &mut $cpu.$reg);
   };
 
-  (@reghi=$reg:ident $cookie:tt, $cpu:expr, $bus:expr) => {
+  (@reghi=$reg:ident $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => {
     step!(@arg $cookie, &mut RegHi { reg: &mut $cpu.$reg });
   };
 
-  (@regval=$reg:ident $cookie:tt, $cpu:expr, $bus:expr) => {
+  (@regval=$reg:ident $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => {
     step!(@arg $cookie, $cpu.$reg);
   };
 
-  (@rel16 $cookie:tt, $cpu:expr, $bus:expr) => { {
+  (@rel16 $cookie:tt, $cpu:expr, $bus:expr, $modrm:ident) => { {
     let mut buf = [0; 2];
     buf[0] = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
     buf[1] = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
     step!(@arg $cookie, LittleEndian::read_i16(&buf))
   } };
 
+  // Group Decoder
+  (@group $cpu:expr, $bus:expr, $modrm:ident, $code:literal,
+   { $( $subcode:literal =>
+        $name:ident[$($args:ident $(= $argrhs:ident)?),*] / $cycles:literal),*$(,)? } ) => { {
+    let subcode = $modrm & 0x38;
+    match subcode {
+      $( $subcode => step!(@code (), $cpu, $bus, $modrm, $name, $cycles, ($($args $(= $argrhs)?)*)) ),*,
+      _ => unimplemented!("opcode: {:02X} {:02X}({:02X})\ncpu: {:#X?}", $code, $modrm, subcode, $cpu)
+    } }
+  };
+
   // Entry Point
-  (($cpu:expr, $bus:expr) => { $( $code:literal => $name:ident[$($args:ident $(= $argrhs:ident)?),*] / $cycles:literal ),*$(,)? } )  => {
+  (($cpu:expr, $bus:expr) =>
+   { $(
+        $code:literal
+
+        // Non-group opcodes
+        $( $($ext:pat)? =>
+           $name:ident[$($args:ident $(= $argrhs:ident)?),*] / $cycles:literal
+        )?
+
+        // Group opcodes
+        $( : $subcodes:tt )?
+     ),*
+     $(,)? } ) => {
     {
       let opcode = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
+      let modrm: u8; // Type ascription unnecessary but gives better err messages when missing $ext
       match(opcode) {
-        $( $code => step!(@code (), $cpu, $bus, $name, $cycles, ($($args $(= $argrhs)?)*)) ),*,
+        $( $( $code => {
+               $( let $ext = (); /* No-op just to trigger expansion. */
+                  modrm = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus); )?
+                step!(@code (), $cpu, $bus, modrm, $name, $cycles, ($($args $(= $argrhs)?)*))
+              }
+           )?
+           $( $code => {
+                modrm = i8088::next_ip($cpu.cs, &mut $cpu.ip, $bus);
+                step!(@group $cpu, $bus, modrm, $code, $subcodes)
+              }
+           )?
+        ),*,
         _ => unimplemented!("opcode: {:02X}\ncpu: {:#X?}", opcode, $cpu)
       }
     }
@@ -245,6 +329,9 @@ impl i8088 {
   pub fn run(&mut self, bus: &mut Bus) {
     loop {
       step!((self, bus) => {
+        0x8B _ => mov[r16, modrm16] / "2/12+",
+        0x8C: { 0x08 => mov[modrm16, reg=cs] / "2/13+", },
+        0x8E: { 0x18 => mov[reg=ds, modrm16] / "2/12+", },
         0xB4 => mov[reghi=a, d8] / 4,
         0xBA => mov[reg=d, d16] / 4,
         0xC3 => ret[reg=ip, regval=ss, reg=sp, mem] / 20,