diff --git a/cpu/cpu.cpp b/cpu/cpu.cpp
index 7049c78..fd2fcd2 100644
--- a/cpu/cpu.cpp
+++ b/cpu/cpu.cpp
@@ -182,69 +182,53 @@ bool Cpu::decodeCond(u8 cc)
 void Cpu::aluop8(AluOp op, u8 lhs, u8 rhs, u8& out, bool update_carry)
 {
   u16 rhs16 = rhs;
+  u16 res_lower;
   u16 res16;
   u8 res;
 
-  if ((op == ADC || op == SBC) && state.carry)
-    rhs16++;
-
   u16 lhs_lower = lhs & 0x0F;
-  u16 lhs_upper = lhs & 0xF0;
-  u16 rhs_lower = rhs16 & 0x0F;
-  u16 rhs_upper = rhs16 & 0x1F0;
+  u16 rhs_lower = rhs & 0x0F;
+
+  if ((op == ADC || op == SBC) && state.carry)
+    {
+      rhs_lower++;
+      rhs16++;
+    }
 
   switch(op)
     {
     case ADD:
     case ADC:
-      res16 = lhs_lower + rhs_lower;
+      res_lower = lhs_lower + rhs_lower;
+      res16 = lhs + rhs16;
       break;
     case SUB:
     case SBC:
     case CP:
-      res16 = lhs_lower - rhs_lower;
+      res_lower = lhs_lower - rhs_lower;
+      res16 = lhs - rhs16;
       break;
     case AND:
-      res16 = lhs_lower & rhs_lower;
+      res_lower = lhs_lower & rhs_lower;
+      res16 = lhs & rhs16;
       break;
     case OR:
-      res16 = lhs_lower | rhs_lower;
+      res_lower = lhs_lower | rhs_lower;
+      res16 = lhs | rhs16;
       break;
     case XOR:
-      res16 = lhs_lower ^ rhs_lower;
+      res_lower = lhs_lower ^ rhs_lower;
+      res16 = lhs ^ rhs16;
       break;
     }
 
-  state.halfcarry = ((res16 & 0x10) != 0) || op == AND;
+  state.halfcarry = ((res_lower & 0x10) != 0) || op == AND;
   state.subtract = (op == SUB) || (op == SBC) || (op == CP);
 
-  switch(op)
-    {
-    case ADD:
-    case ADC:
-      res16 += lhs_upper + rhs_upper;
-      break;
-    case SUB:
-    case SBC:
-    case CP:
-      res16 += lhs_upper - rhs_upper;
-      break;
-    case AND:
-      res16 |= lhs_upper & rhs_upper;
-      break;
-    case OR:
-      res16 |= lhs_upper | rhs_upper;
-      break;
-    case XOR:
-      res16 |= lhs_upper ^ rhs_upper;
-      break;
-    }
-
-  res = (u8)(res16 & 0xFF);
-
   if(update_carry)
     state.carry = ((res16 & 0x100) != 0);
 
+  res = (u8)(res16 & 0xFF);
   state.zero = (res == 0);
 
   if (op != CP)