diff --git a/src/main/scala/amba/axi4/Delayer.scala b/src/main/scala/amba/axi4/Delayer.scala
new file mode 100644
index 00000000..2ca6d1b2
--- /dev/null
+++ b/src/main/scala/amba/axi4/Delayer.scala
@@ -0,0 +1,83 @@
+// See LICENSE.SiFive for license details.
+
+package freechips.rocketchip.amba.axi4
+
+import Chisel._
+import chisel3.util.IrrevocableIO
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.tilelink.LFSRNoiseMaker
+
+// q is the probability to delay a request
+class AXI4Delayer(q: Double)(implicit p: Parameters) extends LazyModule
+{
+  val node = AXI4AdapterNode()
+  require (0.0 <= q && q < 1)
+
+  lazy val module = new LazyModuleImp(this) {
+    def feed[T <: Data](sink: IrrevocableIO[T], source: IrrevocableIO[T], noise: T) {
+      // irrevocable requires that we not lower valid
+      val hold = RegInit(Bool(false))
+      when (sink.valid)  { hold := Bool(true) }
+      when (sink.fire()) { hold := Bool(false) }
+
+      val allow = hold || UInt((q * 65535.0).toInt) <= LFSRNoiseMaker(16, source.valid)
+      sink.valid := source.valid && allow
+      source.ready := sink.ready && allow
+      sink.bits := source.bits
+      when (!sink.valid) { sink.bits := noise }
+    }
+
+    def anoise[T <: AXI4BundleA](bits: T) {
+      bits.id    := LFSRNoiseMaker(bits.params.idBits)
+      bits.addr  := LFSRNoiseMaker(bits.params.addrBits)
+      bits.len   := LFSRNoiseMaker(bits.params.lenBits)
+      bits.size  := LFSRNoiseMaker(bits.params.sizeBits)
+      bits.burst := LFSRNoiseMaker(bits.params.burstBits)
+      bits.lock  := LFSRNoiseMaker(bits.params.lockBits)
+      bits.cache := LFSRNoiseMaker(bits.params.cacheBits)
+      bits.prot  := LFSRNoiseMaker(bits.params.protBits)
+      bits.qos   := LFSRNoiseMaker(bits.params.qosBits)
+      if (bits.params.userBits > 0)
+        bits.user.get := LFSRNoiseMaker(bits.params.userBits)
+    }
+
+    (node.in zip node.out) foreach { case ((in, _), (out, _)) =>
+      val arnoise = Wire(in.ar.bits)
+      val awnoise = Wire(in.aw.bits)
+      val wnoise  = Wire(in.w .bits)
+      val rnoise  = Wire(in.r .bits)
+      val bnoise  = Wire(in.b .bits)
+
+      anoise(arnoise)
+      anoise(awnoise)
+
+      wnoise.data := LFSRNoiseMaker(wnoise.params.dataBits)
+      wnoise.strb := LFSRNoiseMaker(wnoise.params.dataBits/8)
+      wnoise.last := LFSRNoiseMaker(1)(0)
+
+      rnoise.id   := LFSRNoiseMaker(rnoise.params.idBits)
+      rnoise.data := LFSRNoiseMaker(rnoise.params.dataBits)
+      rnoise.resp := LFSRNoiseMaker(rnoise.params.respBits)
+      rnoise.last := LFSRNoiseMaker(1)(0)
+      if (rnoise.params.userBits > 0)
+        rnoise.user.get := LFSRNoiseMaker(rnoise.params.userBits)
+
+      bnoise.id   := LFSRNoiseMaker(bnoise.params.idBits)
+      bnoise.resp := LFSRNoiseMaker(bnoise.params.respBits)
+      if (bnoise.params.userBits > 0)
+        bnoise.user.get := LFSRNoiseMaker(bnoise.params.userBits)
+
+      feed(out.ar, in.ar, arnoise)
+      feed(out.aw, in.aw, awnoise)
+      feed(out.w,  in.w,   wnoise)
+      feed(in.b,   out.b,  bnoise)
+      feed(in.r,   out.r,  rnoise)
+    }
+  }
+}
+
+object AXI4Delayer
+{
+  def apply(q: Double)(implicit p: Parameters): AXI4Node = LazyModule(new AXI4Delayer(q)).node
+}
diff --git a/src/main/scala/amba/axi4/Nodes.scala b/src/main/scala/amba/axi4/Nodes.scala
index 0c9f7f86..bb96759a 100644
--- a/src/main/scala/amba/axi4/Nodes.scala
+++ b/src/main/scala/amba/axi4/Nodes.scala
@@ -22,8 +22,8 @@ object AXI4Imp extends SimpleNodeImp[AXI4MasterPortParameters, AXI4SlavePortPara
 case class AXI4MasterNode(portParams: Seq[AXI4MasterPortParameters])(implicit valName: ValName) extends SourceNode(AXI4Imp)(portParams)
 case class AXI4SlaveNode(portParams: Seq[AXI4SlavePortParameters])(implicit valName: ValName) extends SinkNode(AXI4Imp)(portParams)
 case class AXI4AdapterNode(
-  masterFn:  AXI4MasterPortParameters => AXI4MasterPortParameters,
-  slaveFn:   AXI4SlavePortParameters  => AXI4SlavePortParameters,
+  masterFn:  AXI4MasterPortParameters => AXI4MasterPortParameters = { m => m },
+  slaveFn:   AXI4SlavePortParameters  => AXI4SlavePortParameters  = { s => s },
   numPorts:  Range.Inclusive = 0 to 999)(
   implicit valName: ValName)
   extends AdapterNode(AXI4Imp)(masterFn, slaveFn, numPorts)