diff --git a/vvp/vpi_callback.cc b/vvp/vpi_callback.cc
index 71ddcb924..153bc54e8 100644
--- a/vvp/vpi_callback.cc
+++ b/vvp/vpi_callback.cc
@@ -761,7 +761,7 @@ void vvp_wire_vec4::get_value(struct t_vpi_value*value)
 
 void vvp_wire_vec8::get_value(struct t_vpi_value*value)
 {
-      assert(0);
+      get_signal_value(value);
 }
 
 void vvp_wire_real::get_value(struct t_vpi_value*value)
diff --git a/vvp/vvp_net.cc b/vvp/vvp_net.cc
index 99565d8e0..f5d11d7ee 100644
--- a/vvp/vvp_net.cc
+++ b/vvp/vvp_net.cc
@@ -206,14 +206,14 @@ vvp_net_fil_t::~vvp_net_fil_t()
       assert(force_link_ == 0);
 }
 
-const vvp_vector4_t* vvp_net_fil_t::filter_vec4(const vvp_vector4_t&val)
+vvp_net_fil_t::prop_t vvp_net_fil_t::filter_vec4(const vvp_vector4_t&val, vvp_vector4_t&)
 {
-      return &val;
+      return PROP;
 }
 
-const vvp_vector8_t* vvp_net_fil_t::filter_vec8(const vvp_vector8_t&val)
+vvp_net_fil_t::prop_t vvp_net_fil_t::filter_vec8(const vvp_vector8_t&val, vvp_vector8_t&)
 {
-      return &val;
+      return PROP;
 }
 
 bool vvp_net_fil_t::filter_real(double&)
diff --git a/vvp/vvp_net.h b/vvp/vvp_net.h
index b42eafb49..964ce5a4e 100644
--- a/vvp/vvp_net.h
+++ b/vvp/vvp_net.h
@@ -1119,14 +1119,17 @@ class vvp_net_fil_t  : public vvp_vpi_callback {
       virtual ~vvp_net_fil_t();
 
     public:
+      enum prop_t { STOP=0, PROP, REPL };
+
 	// Return a non-empty vector if the filter allows an
 	// output. The output result may be different from the
 	// input. If the output is nil, then suppress propagation.
-      virtual const vvp_vector4_t* filter_vec4(const vvp_vector4_t&bit);
-      virtual const vvp_vector8_t* filter_vec8(const vvp_vector8_t&val);
 
 	// Return true if the value is to be propagated, or false if
-	// propagation is suppressed. The value may be edited by the filter.
+	// propagation is suppressed. The value may be edited by the
+	// filter, or overridden by the rep argument if present.
+      virtual prop_t filter_vec4(const vvp_vector4_t&bit, vvp_vector4_t&rep);
+      virtual prop_t filter_vec8(const vvp_vector8_t&val, vvp_vector8_t&rep);
       virtual bool filter_real(double&val);
       virtual bool filter_long(long&val);
 
@@ -1162,7 +1165,7 @@ class vvp_net_fil_t  : public vvp_vpi_callback {
 	// currently forced value, and the buf is a value that this
 	// method will use to hold a filtered value, if needed. This
 	// method returns a pointer to val or buf.
-      template <class T> const T*filter_mask_(const T&val, const T&force, T&buf);
+      template <class T> prop_t filter_mask_(const T&val, const T&force, T&rep);
 	// This template method is a scalar value of the above. It
 	// leaves the val, or it replaces it iwth a forced value.
 	// (Not really implemented, yet.)
@@ -1440,11 +1443,22 @@ inline void vvp_net_t::send_vec8_pv(const vvp_vector8_t&val,
 
 inline void vvp_net_t::send_vec4(const vvp_vector4_t&val, vvp_context_t context)
 {
-      const vvp_vector4_t*val_out = fil? fil->filter_vec4(val) : &val;
-      if (val_out == 0)
+      if (fil == 0) {
+	    vvp_send_vec4(out_, val, context);
 	    return;
+      }
 
-      vvp_send_vec4(out_, *val_out, context);
+      vvp_vector4_t rep;
+      switch (fil->filter_vec4(val, rep)) {
+	  case vvp_net_fil_t::STOP:
+	    break;
+	  case vvp_net_fil_t::PROP:
+	    vvp_send_vec4(out_, val, context);
+	    break;
+	  case vvp_net_fil_t::REPL:
+	    vvp_send_vec4(out_, rep, context);
+	    break;
+      }
 }
 
 inline void vvp_net_t::send_vec4_pv(const vvp_vector4_t&val,
@@ -1456,11 +1470,22 @@ inline void vvp_net_t::send_vec4_pv(const vvp_vector4_t&val,
 
 inline void vvp_net_t::send_vec8(const vvp_vector8_t&val)
 {
-      const vvp_vector8_t*val_out = fil? fil->filter_vec8(val) : &val;
-      if (val_out == 0)
+      if (fil == 0) {
+	    vvp_send_vec8(out_, val);
 	    return;
+      }
 
-      vvp_send_vec8(out_, *val_out);
+      vvp_vector8_t rep;
+      switch (fil->filter_vec8(val, rep)) {
+	  case vvp_net_fil_t::STOP:
+	    break;
+	  case vvp_net_fil_t::PROP:
+	    vvp_send_vec8(out_, val);
+	    break;
+	  case vvp_net_fil_t::REPL:
+	    vvp_send_vec8(out_, rep);
+	    break;
+      }
 }
 
 inline void vvp_net_t::send_real(double val, vvp_context_t context)
diff --git a/vvp/vvp_net_sig.cc b/vvp/vvp_net_sig.cc
index b46f26c32..745185038 100644
--- a/vvp/vvp_net_sig.cc
+++ b/vvp/vvp_net_sig.cc
@@ -30,7 +30,7 @@
 
 # include  <iostream>
 
-template <class T> const T*vvp_net_fil_t::filter_mask_(const T&val, const T&force, T&filter)
+template <class T> vvp_net_fil_t::prop_t vvp_net_fil_t::filter_mask_(const T&val, const T&force, T&filter)
 {
       if (!test_force_mask_is_zero()) {
 	    bool propagate_flag = force_propagate_;
@@ -48,14 +48,14 @@ template <class T> const T*vvp_net_fil_t::filter_mask_(const T&val, const T&forc
 
 	    if (propagate_flag) {
 		  run_vpi_callbacks();
-		  return &filter;
+		  return REPL;
 	    } else {
-		  return 0;
+		  return STOP;
 	    }
 
       } else {
 	    run_vpi_callbacks();
-	    return &val;
+	    return PROP;
       }
 }
 
@@ -75,24 +75,6 @@ double vvp_signal_value::real_value() const
       return 0;
 }
 
-#if 0
-const vvp_vector4_t* vvp_fun_signal4::filter_vec4(const vvp_vector4_t&val)
-{
-      return filter_mask_(val, force4_, filter4_);
-}
-#endif
-#if 0
-const vvp_vector8_t* vvp_fun_signal8::filter_vec8(const vvp_vector8_t&val)
-{
-      return filter_mask_(val, force8_, filter8_);
-}
-#endif
-#if 0
-bool vvp_fun_signal_real::filter_real(double&val)
-{
-      return filter_mask_(val);
-}
-#endif
 unsigned vvp_fun_signal_real::filter_size() const
 {
       return size();
@@ -876,19 +858,18 @@ vvp_wire_vec4::vvp_wire_vec4(unsigned wid, vvp_bit4_t init)
 {
 }
 
-const vvp_vector4_t* vvp_wire_vec4::filter_vec4(const vvp_vector4_t&bit)
+vvp_net_fil_t::prop_t vvp_wire_vec4::filter_vec4(const vvp_vector4_t&bit, vvp_vector4_t&rep)
 {
 	// Keep track of the value being driven from this net, even if
 	// it is not ultimately what survives the force filter.
       bits4_ = bit;
-      const vvp_vector4_t*tmp = filter_mask_(bit, force4_, filter4_);
-      return tmp;
+      return filter_mask_(bit, force4_, rep);
 }
 
-const vvp_vector8_t* vvp_wire_vec4::filter_vec8(const vvp_vector8_t&bit)
+vvp_net_fil_t::prop_t vvp_wire_vec4::filter_vec8(const vvp_vector8_t&bit, vvp_vector8_t&)
 {
       assert(0);
-      return 0;
+      return PROP;
 }
 
 unsigned vvp_wire_vec4::filter_size() const
@@ -951,17 +932,17 @@ unsigned vvp_wire_vec4::value_size() const
       return width_;
 }
 
-vvp_bit4_t vvp_wire_vec4::filtered_value_(const vvp_vector4_t&val, unsigned idx) const
+vvp_bit4_t vvp_wire_vec4::filtered_value_(unsigned idx) const
 {
       if (test_force_mask(idx))
 	    return force4_.value(idx);
       else
-	    return val.value(idx);
+	    return bits4_.value(idx);
 }
 
 vvp_bit4_t vvp_wire_vec4::value(unsigned idx) const
 {
-      return filtered_value_(bits4_, idx);
+      return filtered_value_(idx);
 }
 
 vvp_scalar_t vvp_wire_vec4::scalar_value(unsigned idx) const
@@ -973,7 +954,7 @@ vvp_vector4_t vvp_wire_vec4::vec4_value() const
 {
       vvp_vector4_t tmp = bits4_;
       for (unsigned idx = 0 ; idx < bits4_.size() ; idx += 1)
-	    tmp.set_bit(idx, filtered_value_(bits4_, idx));
+	    tmp.set_bit(idx, filtered_value_(idx));
       return tmp;
 }
 
@@ -982,19 +963,25 @@ vvp_wire_vec8::vvp_wire_vec8(unsigned wid)
 {
 }
 
-const vvp_vector4_t* vvp_wire_vec8::filter_vec4(const vvp_vector4_t&bit)
+vvp_net_fil_t::prop_t vvp_wire_vec8::filter_vec4(const vvp_vector4_t&bit, vvp_vector4_t&rep)
 {
-      assert(0);
-      return 0;
+	// QUESTION: Is it really correct to propagate a vec4 if this
+	// is a vec8 node? In fact, it is really possible for a vec4
+	// value to get through to a vec8 filter?
+      vvp_vector8_t rep8;
+      prop_t rc = filter_vec8(vvp_vector8_t(bit,6,6), rep8);
+      if (rc == REPL)
+	    rep = reduce4(rep8);
+
+      return rc;
 }
 
-const vvp_vector8_t* vvp_wire_vec8::filter_vec8(const vvp_vector8_t&bit)
+vvp_net_fil_t::prop_t vvp_wire_vec8::filter_vec8(const vvp_vector8_t&bit, vvp_vector8_t&rep)
 {
 	// Keep track of the value being driven from this net, even if
 	// it is not ultimately what survives the force filter.
       bits8_ = bit;
-      const vvp_vector8_t*tmp = filter_mask_(bit, force8_, filter8_);
-      return tmp;
+      return filter_mask_(bit, force8_, rep);
 }
 
 unsigned vvp_wire_vec8::filter_size() const
@@ -1046,19 +1033,35 @@ unsigned vvp_wire_vec8::value_size() const
       return width_;
 }
 
+vvp_scalar_t vvp_wire_vec8::filtered_value_(unsigned idx) const
+{
+      if (test_force_mask(idx))
+	    return force8_.value(idx);
+      else
+	    return bits8_.value(idx);
+}
+
 vvp_bit4_t vvp_wire_vec8::value(unsigned idx) const
 {
-      assert(0);
+      return filtered_value_(idx).value();
 }
 
 vvp_scalar_t vvp_wire_vec8::scalar_value(unsigned idx) const
 {
-      assert(0);
+      return filtered_value_(idx);
+}
+
+vvp_vector8_t vvp_wire_vec8::vec8_value() const
+{
+      vvp_vector8_t tmp = bits8_;
+      for (unsigned idx = 0 ; idx < bits8_.size() ; idx += 1)
+	    tmp.set_bit(idx, filtered_value_(idx));
+      return tmp;
 }
 
 vvp_vector4_t vvp_wire_vec8::vec4_value() const
 {
-      assert(0);
+      return reduce4(vec8_value());
 }
 
 vvp_wire_real::vvp_wire_real()
diff --git a/vvp/vvp_net_sig.h b/vvp/vvp_net_sig.h
index 64662edfa..93d83aa20 100644
--- a/vvp/vvp_net_sig.h
+++ b/vvp/vvp_net_sig.h
@@ -127,7 +127,6 @@ class vvp_fun_signal4 : public vvp_fun_signal_vec {
       void force_fil_vec4(const vvp_vector4_t&val, vvp_vector2_t mask);
       void force_fil_vec8(const vvp_vector8_t&val, vvp_vector2_t mask);
       void force_fil_real(double val, vvp_vector2_t mask);
-      const vvp_vector4_t* filter_vec4(const vvp_vector4_t&val);
 
 	// Test the value against the filter.
       vvp_bit4_t filtered_value(const vvp_vector4_t&val, unsigned idx) const;
@@ -246,7 +245,6 @@ class vvp_fun_signal8  : public vvp_fun_signal_vec {
       void force_fil_vec4(const vvp_vector4_t&val, vvp_vector2_t mask);
       void force_fil_vec8(const vvp_vector8_t&val, vvp_vector2_t mask);
       void force_fil_real(double val, vvp_vector2_t mask);
-      const vvp_vector8_t* filter_vec8(const vvp_vector8_t&val);
 	// Test the value against the filter.
       vvp_scalar_t filtered_value(const vvp_vector8_t&val, unsigned idx) const;
       const vvp_vector8_t& filtered_vec8(const vvp_vector8_t&val) const;
@@ -274,7 +272,6 @@ class vvp_fun_signal_real : public vvp_fun_signal_base {
       void force_fil_vec8(const vvp_vector8_t&val, vvp_vector2_t mask);
       void force_fil_real(double val, vvp_vector2_t mask);
 
-      bool filter_real(double&val);
 	// Test the value against the filter.
       double filtered_real(double val) const;
 
@@ -361,8 +358,8 @@ class vvp_wire_vec4 : public vvp_wire_base {
 	// the value that the node is driven to, and applies the firce
 	// filters. In wires, this also saves the driven value, so
 	// that when a force is released, we can revert to the driven value.
-      const vvp_vector4_t* filter_vec4(const vvp_vector4_t&bit);
-      const vvp_vector8_t* filter_vec8(const vvp_vector8_t&val);
+      prop_t filter_vec4(const vvp_vector4_t&bit, vvp_vector4_t&rep);
+      prop_t filter_vec8(const vvp_vector8_t&val, vvp_vector8_t&rep);
 
 	// Abstract methods from vvp_vpi_callback
       void get_value(struct t_vpi_value*value);
@@ -381,13 +378,12 @@ class vvp_wire_vec4 : public vvp_wire_base {
       vvp_vector4_t vec4_value() const;
 
     private:
-      vvp_bit4_t filtered_value_(const vvp_vector4_t&val, unsigned idx) const;
+      vvp_bit4_t filtered_value_(unsigned idx) const;
 
     private:
       unsigned width_;
       vvp_vector4_t bits4_; // The tracked driven value
       vvp_vector4_t force4_; // the value being forced
-      vvp_vector4_t filter4_; // scratch space for filter_mask_ function.
 };
 
 class vvp_wire_vec8 : public vvp_wire_base {
@@ -396,8 +392,8 @@ class vvp_wire_vec8 : public vvp_wire_base {
       vvp_wire_vec8(unsigned wid);
 
 	// The main filter behavior for this class
-      const vvp_vector4_t* filter_vec4(const vvp_vector4_t&bit);
-      const vvp_vector8_t* filter_vec8(const vvp_vector8_t&val);
+      prop_t filter_vec4(const vvp_vector4_t&bit, vvp_vector4_t&rep);
+      prop_t filter_vec8(const vvp_vector8_t&val, vvp_vector8_t&rep);
 
 	// Abstract methods from vvp_vpi_callback
       void get_value(struct t_vpi_value*value);
@@ -414,12 +410,16 @@ class vvp_wire_vec8 : public vvp_wire_base {
       vvp_bit4_t value(unsigned idx) const;
       vvp_scalar_t scalar_value(unsigned idx) const;
       vvp_vector4_t vec4_value() const;
+	// This is new to vvp_wire_vec8
+      vvp_vector8_t vec8_value() const;
+
+    private:
+      vvp_scalar_t filtered_value_(unsigned idx) const;
 
     private:
       unsigned width_;
       vvp_vector8_t bits8_;
       vvp_vector8_t force8_; // the value being forced
-      vvp_vector8_t filter8_; // scratch space for filter_mask_ function.
 };
 
 class vvp_wire_real : public vvp_wire_base {