diff --git a/rocket/src/main/scala/dtlb.scala b/rocket/src/main/scala/dtlb.scala
index 6c0af2a0..eb7a91cf 100644
--- a/rocket/src/main/scala/dtlb.scala
+++ b/rocket/src/main/scala/dtlb.scala
@@ -118,12 +118,9 @@ class rocketDTLB(entries: Int) extends Component
   }
  
   // high if there are any unused (invalid) entries in the TLB
-  val invalid_entry = (tag_cam.io.valid_bits != ~Bits(0,entries));
-  val ie_enc = new priorityEncoder(entries);
-  ie_enc.io.in := ~tag_cam.io.valid_bits.toUFix;
-  val ie_addr = ie_enc.io.out;
-  
-  val repl_waddr = Mux(invalid_entry, ie_addr, repl_count).toUFix;
+  val has_invalid_entry = !tag_cam.io.valid_bits.andR
+  val invalid_entry = PriorityEncoder(~tag_cam.io.valid_bits)
+  val repl_waddr = Mux(has_invalid_entry, invalid_entry, repl_count).toUFix;
   
   val lookup = (state === s_ready) && r_cpu_req_val && !io.cpu_req.bits.kill && (req_load || req_store || req_amo || req_pf);
   val lookup_hit  = lookup && tag_hit;
@@ -136,7 +133,7 @@ class rocketDTLB(entries: Int) extends Component
   when (tlb_miss) {
     r_refill_tag := lookup_tag;
     r_refill_waddr := repl_waddr;
-    when (!invalid_entry) {
+    when (!has_invalid_entry) {
       repl_count := repl_count + UFix(1);
     }
   }
diff --git a/rocket/src/main/scala/itlb.scala b/rocket/src/main/scala/itlb.scala
index 231010b9..06cd6e2b 100644
--- a/rocket/src/main/scala/itlb.scala
+++ b/rocket/src/main/scala/itlb.scala
@@ -146,12 +146,9 @@ class rocketITLB(entries: Int) extends Component
   }
  
   // high if there are any unused entries in the ITLB
-  val invalid_entry = (tag_cam.io.valid_bits != ~Bits(0,entries));
-  val ie_enc = new priorityEncoder(entries);
-  ie_enc.io.in := ~tag_cam.io.valid_bits.toUFix;
-  val ie_addr = ie_enc.io.out;
-  
-  val repl_waddr = Mux(invalid_entry, ie_addr, repl_count).toUFix;
+  val has_invalid_entry = !tag_cam.io.valid_bits.andR
+  val invalid_entry = PriorityEncoder(~tag_cam.io.valid_bits)
+  val repl_waddr = Mux(has_invalid_entry, invalid_entry, repl_count).toUFix;
   
   val lookup = (state === s_ready) && r_cpu_req_val;
   val lookup_hit  = lookup && tag_hit;
@@ -162,7 +159,7 @@ class rocketITLB(entries: Int) extends Component
   when (tlb_miss) {
     r_refill_tag := lookup_tag;
     r_refill_waddr := repl_waddr;
-    when (!invalid_entry) {
+    when (!has_invalid_entry) {
       repl_count := repl_count + UFix(1);
     }
   }
diff --git a/rocket/src/main/scala/nbdcache.scala b/rocket/src/main/scala/nbdcache.scala
index 50dd9fc3..57d223b6 100644
--- a/rocket/src/main/scala/nbdcache.scala
+++ b/rocket/src/main/scala/nbdcache.scala
@@ -361,10 +361,8 @@ class ReplayUnit extends Component {
     val cpu_resp_tag = Bits(DCACHE_TAG_BITS, OUTPUT)
   }
 
-  val sdq_val = Reg(resetVal = UFix(0, NSDQ))
-  val sdq_allocator = new priorityEncoder(NSDQ)
-  sdq_allocator.io.in := ~sdq_val
-  val sdq_alloc_id = sdq_allocator.io.out.toUFix
+  val sdq_val = Reg(resetVal = UFix(0))
+  val sdq_alloc_id = PriorityEncoder(~sdq_val(NSDQ-1,0))
 
   val replay_val = Reg(resetVal = Bool(false))
   val replay_retry = replay_val && !io.data_req.ready
diff --git a/rocket/src/main/scala/queues.scala b/rocket/src/main/scala/queues.scala
index 14f416ba..12f4aeae 100644
--- a/rocket/src/main/scala/queues.scala
+++ b/rocket/src/main/scala/queues.scala
@@ -53,3 +53,37 @@ class queue[T <: Data](entries: Int, pipe: Boolean = false, flushable: Boolean =
   io.enq.ready := !maybe_full || enq_ptr != deq_ptr || (if (pipe) io.deq.ready else Bool(false))
   io.deq.bits <> Mem(entries, do_enq, enq_ptr, io.enq.bits).read(deq_ptr)
 }
+
+object Queue
+{
+  def apply[T <: Data](enq: ioDecoupled[T], entries: Int = 2, pipe: Boolean = false) = {
+    val q = (new queue(entries, pipe)) { enq.bits.clone }
+    q.io.enq <> enq
+    q.io.deq
+  }
+}
+
+class pipereg[T <: Data]()(data: => T) extends Component
+{
+  val io = new Bundle {
+    val enq = new ioValid()(data)
+    val deq = new ioValid()(data).flip
+  }
+
+  //val bits = Reg() { io.enq.bits.clone }
+  //when (io.enq.valid) {
+  //  bits := io.enq.bits
+  //}
+
+  io.deq.valid := Reg(io.enq.valid, resetVal = Bool(false))
+  io.deq.bits <> Mem(1, io.enq.valid, UFix(0), io.enq.bits).read(UFix(0))
+}
+
+object PipeReg
+{
+  def apply[T <: Data](enq: ioValid[T]) = {
+    val q = (new pipereg) { enq.bits.clone }
+    q.io.enq <> enq
+    q.io.deq
+  }
+}
diff --git a/rocket/src/main/scala/top.scala b/rocket/src/main/scala/top.scala
index 7a472a94..52925b3e 100644
--- a/rocket/src/main/scala/top.scala
+++ b/rocket/src/main/scala/top.scala
@@ -27,25 +27,14 @@ class Top() extends Component {
   arbiter.io.requestor(2) <> htif.io.mem
 
   val hub = new CoherenceHubNull
-  // connect tile to hub (figure out how to do this more compactly)
-  val xact_init_q = (new queue(2)) { new TransactionInit }
-  xact_init_q.io.enq <> arbiter.io.mem.xact_init
-  xact_init_q.io.deq <> hub.io.tile.xact_init
-  val xact_init_data_q = (new queue(2)) { new TransactionInitData }
-  xact_init_data_q.io.enq <> arbiter.io.mem.xact_init_data
-  xact_init_data_q.io.deq <> hub.io.tile.xact_init_data
-  val xact_rep_q = (new queue(1, pipe = true)) { new TransactionReply }
-  xact_rep_q.io.enq <> hub.io.tile.xact_rep
-  xact_rep_q.io.deq <> arbiter.io.mem.xact_rep
+  // connect tile to hub
+  hub.io.tile.xact_init <> Queue(arbiter.io.mem.xact_init)
+  hub.io.tile.xact_init_data <> Queue(arbiter.io.mem.xact_init_data)
+  arbiter.io.mem.xact_rep <> Queue(hub.io.tile.xact_rep, 1, pipe = true)
   // connect hub to memory
-  val mem_req_q = (new queue(2)) { new MemReqCmd }
-  mem_req_q.io.enq <> hub.io.mem.req_cmd
-  mem_req_q.io.deq <> io.mem.req_cmd
-  val mem_req_data_q = (new queue(2)) { new MemData }
-  mem_req_data_q.io.enq <> hub.io.mem.req_data
-  mem_req_data_q.io.deq <> io.mem.req_data
-  hub.io.mem.resp.valid := Reg(io.mem.resp.valid, resetVal = Bool(false))
-  hub.io.mem.resp.bits := Reg(io.mem.resp.bits)
+  io.mem.req_cmd <> Queue(hub.io.mem.req_cmd)
+  io.mem.req_data <> Queue(hub.io.mem.req_data)
+  hub.io.mem.resp <> PipeReg(io.mem.resp)
 
 
   if (HAVE_VEC)
diff --git a/rocket/src/main/scala/util.scala b/rocket/src/main/scala/util.scala
index 47361d2e..1856a3ba 100644
--- a/rocket/src/main/scala/util.scala
+++ b/rocket/src/main/scala/util.scala
@@ -166,14 +166,7 @@ class Mux1H [T <: Data](n: Int)(gen: => T) extends Component
 }
 
 
-
-
-
-
-
-
-
-class ioDecoupled[T <: Data]()(data: => T) extends Bundle
+class ioDecoupled[+T <: Data]()(data: => T) extends Bundle
 {
   val valid = Bool(INPUT)
   val ready = Bool(OUTPUT)
@@ -211,46 +204,51 @@ class Arbiter[T <: Data](n: Int)(data: => T) extends Component {
   dout <> io.out.bits
 }
 
-class ioPriorityDecoder(in_width: Int, out_width: Int) extends Bundle
-{
-  val in  = UFix(in_width, INPUT);
-  val out = Bits(out_width, OUTPUT);
+class ioLockingArbiter[T <: Data](n: Int)(data: => T) extends Bundle {
+  val in   = Vec(n) { (new ioDecoupled()) { data } }
+  val lock = Vec(n) { Bool() }
+  val out  = (new ioDecoupled()) { data }.flip()
 }
 
-class priorityDecoder(width: Int) extends Component
-{
-  val in_width = ceil(log10(width)/log10(2)).toInt;  
-  val io = new ioPriorityEncoder(in_width, width);
-  val l_out = Wire() { Bits() };
-  
-  l_out := Bits(0, width);
-  for (i <- width-1 to 0 by -1) {
-    when (io.in === UFix(i, in_width)) {
-      l_out := Bits(1,1) << UFix(i);
+class LockingArbiter[T <: Data](n: Int)(data: => T) extends Component {
+  val io = new ioLockingArbiter(n)(data)
+  val locked = Reg(){ Bits(n) }
+  var dout = Wire(){ data } 
+  var vout = Wire(){ Bool() }
+
+  when((locked && io.lock.toBits).orR) {
+    dout := io.in(0).bits
+    for (i <- 0 until n) {
+      io.in(i).ready := io.out.ready && locked(i)
+      vout := io.in(i).valid && locked(i)
+      dout := Mux(locked(i), io.in(i).bits, dout)
     }
-  }
-  
-  io.out := l_out;
-}
-
-class ioPriorityEncoder(in_width: Int, out_width: Int) extends Bundle
-{
-  val in  = Bits(in_width, INPUT);
-  val out = UFix(out_width, OUTPUT);
-}
-
-class priorityEncoder(width: Int) extends Component
-{
-  val out_width = ceil(log10(width)/log10(2)).toInt;  
-  val io = new ioPriorityDecoder(width, out_width);
-  val l_out = Wire() { UFix() };
-  
-  l_out := UFix(0, out_width);
-  for (i <- width-1 to 1 by -1) {
-    when (io.in(i).toBool) {
-      l_out := UFix(i, out_width);
+  } .otherwise {
+    io.in(0).ready := io.out.ready
+    for (i <- 1 until n) {
+      io.in(i).ready := !io.in(i-1).valid && io.in(i-1).ready
+      locked(i) := !io.in(i-1).valid && io.in(i-1).ready && io.lock(i)
     }
+
+    dout := io.in(n-1).bits
+    for (i <- 1 until n)
+      dout = Mux(io.in(n-1-i).valid, io.in(n-1-i).bits, dout)
+
+    vout := io.in(0).valid
+    for (i <- 1 until n)
+      vout = vout || io.in(i).valid
+  }
+
+  vout <> io.out.valid
+  dout <> io.out.bits
+}
+
+object PriorityEncoder
+{
+  def apply(in: Bits, n: Int = 0): UFix = {
+    if (n >= in.getWidth-1)
+      UFix(n)
+    else
+      Mux(in(n), UFix(n), PriorityEncoder(in, n+1))
   }
-  
-  io.out := l_out;
 }