diff --git a/src/src/pipeline/dispatch/NewDispatchStage.scala b/src/src/pipeline/dispatch/NewDispatchStage.scala
index 14f96e01..7e7585fd 100644
--- a/src/src/pipeline/dispatch/NewDispatchStage.scala
+++ b/src/src/pipeline/dispatch/NewDispatchStage.scala
@@ -12,6 +12,7 @@ import pipeline.dispatch.bundles.ReservationStationBundle
 import pipeline.dispatch.rs.InOrderReservationStation
 import control.enums.ExceptionPos
 import pipeline.dispatch.rs.OutOfOrderReservationStation
+import pipeline.dispatch.rs.SimpleOoOReservationStation
 
 // class DispatchNdPort extends Bundle {
 //   val issueEns = Vec(Param.pipelineNum, Bool())
@@ -57,11 +58,7 @@ class NewDispatchStage(
   val reservationStations = Seq.fill(pipelineNum)(
     Module(
       if (Param.isOutOfOrderIssue)
-        new OutOfOrderReservationStation(
-          Param.Width.Rob._channelLength,
-          1,
-          1,
-          1,
+        new SimpleOoOReservationStation(
           Param.Width.Rob._channelLength,
           true
         )
diff --git a/src/src/pipeline/dispatch/bundles/PreExeInstNdPort.scala b/src/src/pipeline/dispatch/bundles/PreExeInstNdPort.scala
index 4f40220d..317828f1 100644
--- a/src/src/pipeline/dispatch/bundles/PreExeInstNdPort.scala
+++ b/src/src/pipeline/dispatch/bundles/PreExeInstNdPort.scala
@@ -46,21 +46,5 @@ class PreExeInstNdPort(readNum: Int = Param.instRegReadNum) extends Bundle {
 }
 
 object PreExeInstNdPort {
-  def default = (new PreExeInstNdPort).Lit(
-    _.needCsr -> false.B,
-    _.exeSel -> ExeInst.Sel.none,
-    _.exeOp -> ExeInst.Op.nop,
-    _.gprReadPorts -> Vec.Lit(RfAccessInfoNdPort.default, RfAccessInfoNdPort.default),
-    _.gprWritePort -> RfAccessInfoNdPort.default,
-    _.isHasImm -> false.B,
-    _.imm -> 0.U,
-    _.jumpBranchAddr -> zeroWord,
-    _.csrReadEn -> false.B,
-    _.csrWriteEn -> false.B,
-    _.isTlb -> false.B,
-    _.issueEn -> Vec.Lit(Seq.fill(Param.pipelineNum)(false.B): _*),
-    _.isPrivilege -> false.B,
-    _.branchType -> 0.U,
-    _.isBranch -> false.B
-  )
+  def default = 0.U.asTypeOf(new PreExeInstNdPort)
 }
diff --git a/src/src/pipeline/dispatch/rs/OutOfOrderReservationStation.scala b/src/src/pipeline/dispatch/rs/OutOfOrderReservationStation.scala
index a320b8b4..dbfbc2b1 100644
--- a/src/src/pipeline/dispatch/rs/OutOfOrderReservationStation.scala
+++ b/src/src/pipeline/dispatch/rs/OutOfOrderReservationStation.scala
@@ -21,6 +21,8 @@ class OutOfOrderReservationStation(
       channelLength
     ) {
 
+  require(supportCheckForIssue == true)
+
 // Fallback
   io.dequeuePorts.foreach(_ <> DontCare)
   io.enqueuePorts.foreach(_.ready := false.B)
@@ -108,7 +110,7 @@ class OutOfOrderReservationStation(
         //     .contains(elem.bits.regReadPort.preExeInstInfo.exeSel
         elem.bits.regReadPort.preExeInstInfo.forbidOutOfOrder
       ) {
-        if (idx >= enqMaxNum) {
+        if (idx >= deqMaxNum) {
           en := false.B
         } else {
           when(!ramDownViewEnableDeq.take(idx).foldLeft(true.B)(_ && _)) {
diff --git a/src/src/pipeline/dispatch/rs/SimpleOoOReservationStation.scala b/src/src/pipeline/dispatch/rs/SimpleOoOReservationStation.scala
new file mode 100644
index 00000000..6a65c734
--- /dev/null
+++ b/src/src/pipeline/dispatch/rs/SimpleOoOReservationStation.scala
@@ -0,0 +1,177 @@
+package pipeline.dispatch.rs
+
+import chisel3._
+import chisel3.util._
+import pipeline.dispatch.bundles.ReservationStationBundle
+import pipeline.rob.enums.RobDistributeSel
+import utils.MultiCounter
+
+class SimpleOoOReservationStation(
+  queueLength:          Int,
+  supportCheckForIssue: Boolean = true)
+    extends BaseReservationStation(
+      queueLength,
+      1,
+      1,
+      1,
+      queueLength
+    ) {
+
+  require(supportCheckForIssue == true)
+
+// Fallback
+  io.dequeuePorts.foreach(_ <> DontCare)
+  io.enqueuePorts.foreach(_.ready := false.B)
+  io.dequeuePorts.foreach(_.valid := false.B)
+
+  require(queueLength > 1)
+  require(queueLength > 1)
+  require(isPow2(queueLength))
+
+  val ram = RegInit(VecInit(Seq.fill(queueLength)(0.U.asTypeOf(Valid(new ReservationStationBundle)))))
+
+  val enq_ptr = Module(new MultiCounter(queueLength, 1))
+  val deq_ptr = Module(new MultiCounter(queueLength, 1))
+
+  enq_ptr.io.inc   := 0.U
+  enq_ptr.io.flush := io.isFlush
+  deq_ptr.io.inc   := 0.U
+  deq_ptr.io.flush := io.isFlush
+
+  val maybeFull = RegInit(false.B)
+  val ptrMatch  = enq_ptr.io.value === deq_ptr.io.value
+  val isEmpty   = WireDefault(ptrMatch && !maybeFull)
+  val isFull    = WireDefault(ptrMatch && maybeFull)
+
+  io.enqueuePorts.head.ready := !isFull
+
+  val enqEn      = io.enqueuePorts.head.valid && io.enqueuePorts.head.ready
+  val enqueueNum = enqEn.asUInt
+
+  val deqEn      = io.dequeuePorts.head.valid && io.dequeuePorts.head.ready
+  val dequeueNum = deqEn.asUInt
+
+  enq_ptr.io.inc := enqueueNum
+  deq_ptr.io.inc := dequeueNum
+
+  when(enqueueNum > dequeueNum) {
+    maybeFull := true.B
+  }.elsewhen(enqueueNum < dequeueNum) {
+    maybeFull := false.B
+  }
+
+  // dequeue
+  // invalidate which are dequeue
+  when(deqEn) {
+    ram(deq_ptr.io.value).valid := false.B
+  }
+
+  // select which can issue
+  val ramDownView = WireDefault(VecInit(Seq.range(0, queueLength).map { idx =>
+    ram(deq_ptr.io.incResults(idx))
+  }))
+
+  val ramDownViewEnableDeq = Wire(Vec(queueLength, Bool()))
+
+  ramDownViewEnableDeq.lazyZip(ramDownView).zipWithIndex.foreach {
+    case ((en, elem), idx) =>
+      en := elem.valid && elem.bits.robResult.readResults.forall(
+        _.sel === RobDistributeSel.realData
+      )
+      if (idx != 0) {
+        when(elem.bits.regReadPort.preExeInstInfo.forbidOutOfOrder) {
+          en := false.B
+        }
+      }
+  }
+
+  // // select dequeue num of elem to issue
+  val selectedDownViewIndex = PriorityEncoder(ramDownViewEnableDeq)
+
+  io.dequeuePorts.head.valid := ramDownViewEnableDeq(selectedDownViewIndex)
+  io.dequeuePorts.head.bits  := ramDownView(selectedDownViewIndex).bits
+
+  // compress
+  // deq_ptr - out - enq_ptr
+  // for those between deq_ptr and out idx += 1
+  val compressResult = Wire(Vec(queueLength, Valid(new ReservationStationBundle)))
+
+  when(deqEn) {
+    compressResult.zip(ramDownView).foreach {
+      case (dst, src) =>
+        dst.valid := false.B
+        dst.bits  := DontCare
+    }
+    ramDownView.zipWithIndex.foreach {
+      case (elem, src_idx) =>
+        when(src_idx.U === selectedDownViewIndex) {
+          // pass
+        }.elsewhen(src_idx.U < selectedDownViewIndex) {
+          // up one
+          if (src_idx != queueLength - 1) {
+            compressResult(src_idx + 1) := elem
+          }
+        }.otherwise {
+          compressResult(src_idx) := elem
+        }
+    }
+  }.otherwise {
+    compressResult.zip(ramDownView).foreach {
+      case (dst, src) =>
+        dst := src
+    }
+  }
+
+  // // write
+  compressResult.zipWithIndex.foreach {
+    case (src, idx) =>
+      ram(deq_ptr.io.incResults(idx)) := src
+
+      io.writebacks.foreach { wb =>
+        src.bits.regReadPort.preExeInstInfo.gprReadPorts
+          .lazyZip(src.bits.robResult.readResults)
+          .lazyZip(ram(deq_ptr.io.incResults(idx)).bits.robResult.readResults)
+          .foreach {
+            case (readPort, robReadResult, dst) =>
+              when(
+                wb.en && readPort.en &&
+                  robReadResult.sel === RobDistributeSel.robId &&
+                  wb.robId === robReadResult.result
+              ) {
+                dst.sel    := RobDistributeSel.realData
+                dst.result := wb.data
+              }
+          }
+      }
+  }
+
+  // enqueue
+  val in = io.enqueuePorts.head
+  when(enqEn) {
+    ram(enq_ptr.io.value).bits  := in.bits
+    ram(enq_ptr.io.value).valid := true.B
+
+    io.writebacks.foreach { wb =>
+      in.bits.regReadPort.preExeInstInfo.gprReadPorts
+        .lazyZip(in.bits.robResult.readResults)
+        .lazyZip(ram(enq_ptr.io.value).bits.robResult.readResults)
+        .foreach {
+          case (readPort, robReadResult, dst) =>
+            when(
+              wb.en && readPort.en &&
+                robReadResult.sel === RobDistributeSel.robId &&
+                wb.robId === robReadResult.result
+            ) {
+              dst.sel    := RobDistributeSel.realData
+              dst.result := wb.data
+            }
+        }
+    }
+  }
+
+  when(io.isFlush) {
+    ram.foreach(_.valid := false.B)
+    maybeFull := false.B
+  }
+
+}
diff --git a/src/src/pipeline/queue/bundles/DecodeOutNdPort.scala b/src/src/pipeline/queue/bundles/DecodeOutNdPort.scala
index d60aebc9..3ea9475b 100644
--- a/src/src/pipeline/queue/bundles/DecodeOutNdPort.scala
+++ b/src/src/pipeline/queue/bundles/DecodeOutNdPort.scala
@@ -12,8 +12,5 @@ class DecodeOutNdPort extends Bundle {
 }
 
 object DecodeOutNdPort {
-  def default = (new DecodeOutNdPort).Lit(
-    _.isMatched -> false.B,
-    _.info -> PreExeInstNdPort.default
-  )
+  def default = 0.U.asTypeOf(new DecodeOutNdPort)
 }