diff --git a/difftest b/difftest
index 3cb2104b..43a308e8 160000
--- a/difftest
+++ b/difftest
@@ -1 +1 @@
-Subproject commit 3cb2104b27d12b8da5888075544db88613eda714
+Subproject commit 43a308e89ae28dfb52425c26e6995c7db2291daa
diff --git a/src/main/scala/nutcore/RF.scala b/src/main/scala/nutcore/RF.scala
index ad47b01d..0923f199 100644
--- a/src/main/scala/nutcore/RF.scala
+++ b/src/main/scala/nutcore/RF.scala
@@ -29,6 +29,7 @@ trait HasRegFileParameter {
 class RegFile extends HasRegFileParameter with HasNutCoreParameter {
   val rf = Mem(NRReg, UInt(XLEN.W))
   def read(addr: UInt) : UInt = Mux(addr === 0.U, 0.U, rf(addr))
+  def read_all: Seq[UInt] = Seq(0.U) ++ (1 until NRReg).map { idx => rf(idx) }
   def write(addr: UInt, data: UInt) = { rf(addr) := data(XLEN-1,0) }
 } 
 
diff --git a/src/main/scala/nutcore/backend/ooo/Backend.scala b/src/main/scala/nutcore/backend/ooo/Backend.scala
index 97da45fb..ac9ef6e5 100644
--- a/src/main/scala/nutcore/backend/ooo/Backend.scala
+++ b/src/main/scala/nutcore/backend/ooo/Backend.scala
@@ -640,9 +640,9 @@ class Backend_ooo(implicit val p: NutCoreConfig) extends NutCoreModule with HasR
   BoringUtils.addSource(!io.in(0).valid, "perfCntCondMdpNoInst")
 
   if (!p.FPGAPlatform || p.FPGADifftest) {
-    val difftest = DifftestModule(new DiffArchIntRegState)
-    difftest.coreid := 0.U // TODO
-    difftest.value  := VecInit((0 to NRReg-1).map(i => rf.read(i.U)))
+    val difftest = DifftestModule(new DiffPhyIntRegState(NRReg)) // Size = NRREG, use as ArchIntReg
+    difftest.coreid := 0.U
+    difftest.value := VecInit(rf.read_all)
   }
 
   if (!p.FPGAPlatform || p.FPGADifftest) {
diff --git a/src/main/scala/nutcore/backend/ooo/ROB.scala b/src/main/scala/nutcore/backend/ooo/ROB.scala
index 70f279ce..4effc778 100644
--- a/src/main/scala/nutcore/backend/ooo/ROB.scala
+++ b/src/main/scala/nutcore/backend/ooo/ROB.scala
@@ -510,12 +510,6 @@ class ROB(implicit val p: NutCoreConfig) extends NutCoreModule with HasInstrType
       difftest_commit.fpwen    := false.B
       difftest_commit.wdest    := io.wb(i).rfDest
       difftest_commit.wpdest   := io.wb(i).rfDest
-
-      val difftest_wb = DifftestModule(new DiffIntWriteback, delay = 1)
-      difftest_wb.coreid := 0.U
-      difftest_wb.valid := io.wb(i).rfWen && io.wb(i).rfDest =/= 0.U
-      difftest_wb.address := io.wb(i).rfDest
-      difftest_wb.data := io.wb(i).rfData
     }
   } else {
     BoringUtils.addSource(retireATerm, "ilaWBUvalid")
diff --git a/src/main/scala/nutcore/backend/seq/ISU.scala b/src/main/scala/nutcore/backend/seq/ISU.scala
index 3aaeea36..e051c492 100644
--- a/src/main/scala/nutcore/backend/seq/ISU.scala
+++ b/src/main/scala/nutcore/backend/seq/ISU.scala
@@ -99,8 +99,8 @@ class ISU(implicit val p: NutCoreConfig) extends NutCoreModule with HasRegFilePa
   BoringUtils.addSource(WireInit(io.out.fire), "perfCntCondISUIssue")
 
   if (!p.FPGAPlatform || p.FPGADifftest) {
-    val difftest = DifftestModule(new DiffArchIntRegState)
-    difftest.coreid := 0.U // TODO
-    difftest.value  := VecInit((0 to NRReg-1).map(i => rf.read(i.U)))
+    val difftest = DifftestModule(new DiffPhyIntRegState(NRReg)) // Size = NRREG, use as ArchIntReg
+    difftest.coreid := 0.U
+    difftest.value := VecInit(rf.read_all)
   }
 }
diff --git a/src/main/scala/nutcore/backend/seq/WBU.scala b/src/main/scala/nutcore/backend/seq/WBU.scala
index 71da3532..3cdaf8bb 100644
--- a/src/main/scala/nutcore/backend/seq/WBU.scala
+++ b/src/main/scala/nutcore/backend/seq/WBU.scala
@@ -1,17 +1,17 @@
 /**************************************************************************************
 * Copyright (c) 2020 Institute of Computing Technology, CAS
 * Copyright (c) 2020 University of Chinese Academy of Sciences
-* 
+*
 * NutShell is licensed under Mulan PSL v2.
-* You can use this software according to the terms and conditions of the Mulan PSL v2. 
+* You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
-*             http://license.coscl.org.cn/MulanPSL2 
-* 
-* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER 
-* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR 
-* FIT FOR A PARTICULAR PURPOSE.  
+*             http://license.coscl.org.cn/MulanPSL2
+*
+* THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY OR
+* FIT FOR A PARTICULAR PURPOSE.
 *
-* See the Mulan PSL v2 for more details.  
+* See the Mulan PSL v2 for more details.
 ***************************************************************************************/
 
 package nutcore
@@ -57,12 +57,6 @@ class WBU(implicit val p: NutCoreConfig) extends NutCoreModule{
     difftest_commit.fpwen  := false.B
     difftest_commit.wdest  := io.wb.rfDest
     difftest_commit.wpdest := io.wb.rfDest
-
-    val difftest_wb = DifftestModule(new DiffIntWriteback, delay = 1)
-    difftest_wb.coreid  := 0.U
-    difftest_wb.valid   := io.wb.rfWen && io.wb.rfDest =/= 0.U
-    difftest_wb.address := io.wb.rfDest
-    difftest_wb.data    := io.wb.rfData
   } else {
     BoringUtils.addSource(io.in.valid, "ilaWBUvalid")
     BoringUtils.addSource(io.in.bits.decode.cf.pc, "ilaWBUpc")
diff --git a/src/main/scala/sim/NutShellSim.scala b/src/main/scala/sim/NutShellSim.scala
index 51b84872..b175e9b3 100644
--- a/src/main/scala/sim/NutShellSim.scala
+++ b/src/main/scala/sim/NutShellSim.scala
@@ -45,7 +45,8 @@ class NutShellSim extends Module with HasDiffTestInterfaces {
 
   val uart = IO(new UARTIO)
   uart <> mmio.io.uart
-  override def connectTopIOs(difftest: DifftestTopIO): Unit = {
+  override def connectTopIOs(difftest: DifftestTopIO): Seq[Data] = {
     difftest.uart <> uart
+    Seq.empty
   }
 }
diff --git a/src/test/scala/TopMain.scala b/src/test/scala/TopMain.scala
index bd53e61f..4678e81a 100644
--- a/src/test/scala/TopMain.scala
+++ b/src/test/scala/TopMain.scala
@@ -39,9 +39,8 @@ class Top extends Module {
 class FpgaDiffTop extends NutShell()(NutCoreConfig(FPGADifftest = true)) with HasDiffTestInterfaces {
   override def desiredName: String = "NutShell"
   override def cpuName: Option[String] = Some("NutShell")
-  override def connectTopIOs(difftest: DifftestTopIO): Unit = {
-    val io = IO(chiselTypeOf(this.io))
-    io <> this.io
+  override def connectTopIOs(difftest: DifftestTopIO): Seq[Data] = {
+    Seq(io)
   }
 }