diff --git a/gauntlet.s b/gauntlet.s
index 71d5161..ce0c4ae 100644
--- a/gauntlet.s
+++ b/gauntlet.s
@@ -2172,7 +2172,7 @@ return_from_trap2:
   halt
 
 # TODO: Floats
-# TODO: Bitstrings
+# TODO: Bitstring search
 
 #========= I / O ============================
 
@@ -2445,6 +2445,180 @@ movbsu2:
   be 4
   halt
 
+xorbsu:
+  # Set up our test data.
+  movhi hi(0x05000000), r0, r30
+  movea lo(0x05000000), r30, r30
+
+  # Source data
+  movhi hi(0x76543210), r0, r7
+  movea lo(0x76543210), r7, r7
+  st.w r7, 0[r30]
+  movhi hi(0xfedcba98), r0, r7
+  movea lo(0xfedcba98), r7, r7
+  st.w r7, 4[r30]
+  movhi hi(0xdeadbeef), r0, r7
+  movea lo(0xdeadbeef), r7, r7
+  st.w r7, 8[r30]
+
+
+  # Destination at 0x05000100
+  addi 0x100, r30, r29
+
+  # Dst data (set to some known values)
+  movhi hi(0x11111111), r0, r7
+  movea lo(0x11111111), r7, r7
+  st.w r7, 0[r29]
+  st.w r7, 4[r29]
+  st.w r7, 8[r29]
+  st.w r7, 12[r29]
+
+  # Copy 93 bits
+  movea 93, r0, r28
+
+  # Read from bit 4
+  mov 4, r27
+
+  # Write starting at bit 7
+  mov 7, r26
+
+  # Execute
+  xorbsu
+
+  # 0 bits left
+  cmp 0, r28
+  be 4
+  halt
+
+  # Dst offset now 4
+  cmp 4, r26
+  be 4
+  halt
+
+  # Src offset now 1
+  cmp 1, r27
+  be 4
+  halt
+
+  # Now inspect the memory...
+  movhi hi(0x05000100), r0, r29
+  movea lo(0x05000100), r29, r29
+
+  ld.w 0[r29], r6
+  movhi hi(0xA3B08191), r0, r7
+  movea lo(0xA3B08191), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 4[r29], r6
+  movhi hi(0xE7F4C5D2), r0, r7
+  movea lo(0xE7F4C5D2), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 8[r29], r6
+  movhi hi(0xE47CE66E), r0, r7
+  movea lo(0xE47CE66E), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 12[r29], r6
+  movhi hi(0x1111111f), r0, r7
+  movea lo(0x1111111f), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+andnbsu:
+  # Set up our test data.
+  movhi hi(0x05000000), r0, r30
+  movea lo(0x05000000), r30, r30
+
+  # Source data
+  movhi hi(0x76543210), r0, r7
+  movea lo(0x76543210), r7, r7
+  st.w r7, 0[r30]
+  movhi hi(0xfedcba98), r0, r7
+  movea lo(0xfedcba98), r7, r7
+  st.w r7, 4[r30]
+  movhi hi(0xdeadbeef), r0, r7
+  movea lo(0xdeadbeef), r7, r7
+  st.w r7, 8[r30]
+
+
+  # Destination at 0x05000100
+  addi 0x100, r30, r29
+
+  # Dst data (set to some known values)
+  movhi hi(0x11111111), r0, r7
+  movea lo(0x11111111), r7, r7
+  st.w r7, 0[r29]
+  st.w r7, 4[r29]
+  st.w r7, 8[r29]
+  st.w r7, 12[r29]
+
+  # Copy 93 bits
+  movea 93, r0, r28
+
+  # Read from bit 4
+  mov 4, r27
+
+  # Write starting at bit 7
+  mov 7, r26
+
+  # Execute
+  andnbsu
+
+  # 0 bits left
+  cmp 0, r28
+  be 4
+  halt
+
+  # Dst offset now 4
+  cmp 4, r26
+  be 4
+  halt
+
+  # Src offset now 1
+  cmp 1, r27
+  be 4
+  halt
+
+  # Now inspect the memory...
+  movhi hi(0x05000100), r0, r29
+  movea lo(0x05000100), r29, r29
+
+  ld.w 0[r29], r6
+  movhi hi(0x01100111), r0, r7
+  movea lo(0x01100111), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 4[r29], r6
+  movhi hi(0x01100110), r0, r7
+  movea lo(0x01100110), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 8[r29], r6
+  movhi hi(0x00100000), r0, r7
+  movea lo(0x00100000), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
+  ld.w 12[r29], r6
+  movhi hi(0x11111111), r0, r7
+  movea lo(0x11111111), r7, r7
+  cmp r6, r7
+  be 4
+  halt
+
 caxi:
   movhi 0x500, r0, r6
   movea 0x10, r6, r6