diff --git a/vvp/codes.h b/vvp/codes.h
index 6e929e0bd..65b99184a 100644
--- a/vvp/codes.h
+++ b/vvp/codes.h
@@ -112,8 +112,8 @@ extern bool of_FLAG_SET_IMM(vthread_t thr, vvp_code_t code);
 extern bool of_FLAG_SET_VEC4(vthread_t thr, vvp_code_t code);
 extern bool of_FORCE_LINK(vthread_t thr, vvp_code_t code);
 extern bool of_FORCE_VEC4(vthread_t thr, vvp_code_t code);
+extern bool of_FORCE_VEC4_OFF(vthread_t thr, vvp_code_t code);
 extern bool of_FORCE_WR(vthread_t thr, vvp_code_t code);
-extern bool of_FORCE_X0(vthread_t thr, vvp_code_t code);
 extern bool of_FORK(vthread_t thr, vvp_code_t code);
 extern bool of_FREE(vthread_t thr, vvp_code_t code);
 extern bool of_INV(vthread_t thr, vvp_code_t code);
diff --git a/vvp/compile.cc b/vvp/compile.cc
index 7da402e23..737ac117e 100644
--- a/vvp/compile.cc
+++ b/vvp/compile.cc
@@ -159,10 +159,10 @@ static const struct opcode_table_s opcode_table[] = {
       { "%flag_get/vec4", of_FLAG_GET_VEC4, 1, {OA_NUMBER, OA_NONE, OA_NONE} },
       { "%flag_set/imm",  of_FLAG_SET_IMM,  2, {OA_NUMBER, OA_BIT1, OA_NONE} },
       { "%flag_set/vec4", of_FLAG_SET_VEC4, 1, {OA_NUMBER, OA_NONE, OA_NONE} },
-      { "%force/link",of_FORCE_LINK,2,{OA_FUNC_PTR, OA_FUNC_PTR2, OA_NONE} },
-      { "%force/vec4",of_FORCE_VEC4,1,{OA_FUNC_PTR, OA_NONE,      OA_NONE} },
-      { "%force/wr",  of_FORCE_WR,  1,{OA_FUNC_PTR, OA_NONE,      OA_NONE} },
-      { "%force/x0",of_FORCE_X0,3,{OA_FUNC_PTR, OA_BIT1,     OA_BIT2} },
+      { "%force/link",    of_FORCE_LINK,2,{OA_FUNC_PTR, OA_FUNC_PTR2, OA_NONE} },
+      { "%force/vec4",    of_FORCE_VEC4,    1,{OA_FUNC_PTR, OA_NONE,      OA_NONE} },
+      { "%force/vec4/off",of_FORCE_VEC4_OFF,2,{OA_FUNC_PTR, OA_BIT1,      OA_NONE} },
+      { "%force/wr",      of_FORCE_WR,      1,{OA_FUNC_PTR, OA_NONE,      OA_NONE} },
       { "%free",   of_FREE,   1,  {OA_VPI_PTR,  OA_NONE,     OA_NONE} },
       { "%inv",    of_INV,    0,  {OA_NONE,     OA_NONE,     OA_NONE} },
       { "%ix/add", of_IX_ADD, 3,  {OA_NUMBER,   OA_BIT1,     OA_BIT2} },
diff --git a/vvp/opcodes.txt b/vvp/opcodes.txt
index 3779dc1c7..ef3202425 100644
--- a/vvp/opcodes.txt
+++ b/vvp/opcodes.txt
@@ -556,27 +556,21 @@ These instructions provide a means for accessing flag bits. The
 stack, and the %flag_set/vec4 pops the top of the vec4 stack and
 writes the LSB to the selected flag.
 
-* %force/v <label>, <bit>, <wid>
+* %force/vec4 <label>
+* %force/vec4/off <label>, <off>
 
-Force a constant value to the target variable. This is similar to %set
-and %cassign/vec4, but it uses the force port (port-2) of the signal
-functor instead of the normal assign port (port-0), so the signal
-responds differently. See "VARIABLE STATEMENTS" and "NET STATEMENTS"
-in the README.txt file.
+Perform a "force" assign of a values to the tarvet variable. The value
+to be forced is popped from the vec4 stack and forced to the target
+variable. The /off variant forces a part of a vector. The width of the
+part comes from the width of the popped value, and the <off> is an
+index register that contains the cannonical offset where the value
+sets written.
 
 * %force/wr <var-label>
 
 Force a constant real value to the target variable. See %force/v
 above. The value is popped from the real value stack.
 
-* %force/x0 <label>, <bit>, <wid>
-
-Force a constant value to part of the target variable. This is similar
-to %set/x instruction, but it uses the force port (port-2) of the signal
-functor instead of the normal assign port (port-0), so the signal
-responds differently. See "VARIABLE STATEMENTS" and "NET STATEMENTS"
-in the README.txt file.
-
 * %fork <code-label>, <scope-label>
 
 This instruction is similar to %jmp, except that it creates a new
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 9e58bfc70..2d91c53a7 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -3008,6 +3008,43 @@ bool of_FORCE_VEC4(vthread_t thr, vvp_code_t cp)
       return true;
 }
 
+/*
+ * %force/vec4/off <net>, <off>
+ */
+bool of_FORCE_VEC4_OFF(vthread_t thr, vvp_code_t cp)
+{
+      vvp_net_t*net = cp->net;
+      unsigned base_idx = cp->bit_idx[0];
+      long base = thr->words[base_idx].w_int;
+      vvp_vector4_t value = thr->pop_vec4();
+      unsigned wid = value.size();
+
+      assert(net->fil);
+
+	// This is the width of the target vector.
+      unsigned use_size = net->fil->filter_size();
+
+      if (base >= (long)use_size)
+	    return true;
+      if (base < -(long)use_size)
+	    return true;
+
+      if ((base + wid) > use_size)
+	    wid = use_size - base;
+
+	// Make a mask of which bits are to be forced, 0 for unforced
+	// bits and 1 for forced bits.
+      vvp_vector2_t mask (vvp_vector2_t::FILL0, use_size);
+      for (unsigned idx = 0 ; idx < wid ; idx += 1)
+	    mask.set_bit(base+idx, 1);
+
+      vvp_vector4_t tmp (use_size, BIT4_Z);
+      tmp.set_vec(base, value);
+
+      net->force_vec4(tmp, mask);
+      return true;
+}
+
 bool of_FORCE_WR(vthread_t thr, vvp_code_t cp)
 {
       vvp_net_t*net  = cp->net;
@@ -3018,52 +3055,6 @@ bool of_FORCE_WR(vthread_t thr, vvp_code_t cp)
       return true;
 }
 
-
-bool of_FORCE_X0(vthread_t thr, vvp_code_t cp)
-{
-#if 0
-      vvp_net_t*net = cp->net;
-      unsigned base = cp->bit_idx[0];
-      unsigned wid = cp->bit_idx[1];
-
-      assert(net->fil);
-
-	// Implicitly, we get the base into the target vector from the
-	// X0 register.
-      long index = thr->words[0].w_int;
-
-      if (index < 0 && (wid <= (unsigned)-index))
-	    return true;
-
-      if (index < 0) {
-	    wid -= (unsigned) -index;
-	    index = 0;
-      }
-
-      unsigned use_size = net->fil->filter_size();
-
-
-      if (index >= (long)use_size)
-	    return true;
-
-      if (index+wid > use_size)
-	    wid = use_size - index;
-
-      vvp_vector2_t mask(vvp_vector2_t::FILL0, use_size);
-      for (unsigned idx = 0 ; idx < wid ; idx += 1)
-	    mask.set_bit(index+idx, 1);
-
-      vvp_vector4_t vector = vthread_bits_to_vector(thr, base, wid);
-      vvp_vector4_t value(use_size, BIT4_Z);
-      value.set_vec(index, vector);
-
-      net->force_vec4(value, mask);
-#else
-      fprintf(stderr, "XXXX NOT IMPLEMENTED: %%force/x0 ...\n");
-#endif
-      return true;
-}
-
 /*
  * The %fork instruction causes a new child to be created and pushed
  * in front of any existing child. This causes the new child to be