diff --git a/.gitignore b/.gitignore
index d7450221f8590013e86a57bd2ff6a7d6e9b282d1..2d64a9d610abcd5ea1546999ee495703d2ca607a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -351,3 +351,12 @@ stale_outputs_checked
 *.snapshot
 __pycache__
 overnight.sh
+
+# VCS files
+simv
+simv.daidir
+ucli.key
+stack.info*
+*.vpd
+*.bin
+
diff --git a/Makefile b/Makefile
index d563b4a46ecd5c29031f0912da991edf05cf9577..a3e41c35f6c71f63fe542583d3d606fb51ee3874 100644
--- a/Makefile
+++ b/Makefile
@@ -77,34 +77,10 @@ SIM_CXXFILES = $(shell find $(SIM_CSRC_DIR) -name "*.cpp")
 DIFFTEST_CSRC_DIR = $(abspath ./src/test/csrc/difftest)
 DIFFTEST_CXXFILES = $(shell find $(DIFFTEST_CSRC_DIR) -name "*.cpp")
 
-SIM_VSRC = $(shell find ./src/test/vsrc -name "*.v" -or -name "*.sv")
+SIM_VSRC = $(shell find ./src/test/vsrc/common -name "*.v" -or -name "*.sv")
 
-include Makefile.emu
-
-EMU_VCS := simv
-
-VCS_SRC_FILE = $(TOP_V) \
-               $(BUILD_DIR)/plusarg_reader.v \
-               $(BUILD_DIR)/SDHelper.v
-
-VCS_TB_DIR = $(abspath ./src/test/vcs)
-VCS_TB_FILE = $(shell find $(VCS_TB_DIR) -name "*.c") \
-              $(shell find $(VCS_TB_DIR) -name "*.v")
-
-VCS_OPTS := -full64 +v2k -timescale=1ns/10ps \
-  -LDFLAGS -Wl,--no-as-needed \
-  -sverilog \
-  +lint=TFIPC-L \
-  -debug_all +vcd+vcdpluson \
-  +define+RANDOMIZE_GARBAGE_ASSIGN \
-  +define+RANDOMIZE_INVALID_ASSIGN \
-  +define+RANDOMIZE_REG_INIT \
-  +define+RANDOMIZE_MEM_INIT \
-  +define+RANDOMIZE_DELAY=1
-
-$(EMU_VCS): $(VCS_SRC_FILE) $(VCS_TB_FILE)
-	rm -rf csrc
-	vcs $(VCS_OPTS) $(VCS_SRC_FILE) $(VCS_TB_FILE)
+include verilator.mk
+include vcs.mk
 
 ifndef NEMU_HOME
 $(error NEMU_HOME is not set)
@@ -150,7 +126,7 @@ cache:
 release-lock:
 	ssh -tt $(REMOTE) 'rm -f $(LOCK)'
 
-clean:
+clean: vcs-clean
 	rm -rf ./build
 
 init:
diff --git a/src/test/csrc/vcs/main.cpp b/src/test/csrc/vcs/main.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..1ec16409b12a49aa4704806b44718e0af4a79a0f
--- /dev/null
+++ b/src/test/csrc/vcs/main.cpp
@@ -0,0 +1,27 @@
+#include <common.h>
+#include <locale.h>
+#include "difftest.h"
+#include "device.h"
+#include "goldenmem.h"
+#include "ram.h"
+
+static bool has_reset = false;
+
+extern "C" void simv_init() {
+  printf("simv compiled at %s, %s\n", __DATE__, __TIME__);
+  setlocale(LC_NUMERIC, "");
+
+  init_goldenmem();
+  difftest_init();
+  init_device();
+
+  assert_init();
+  init_ram("ram.bin");
+
+}
+
+extern "C" void simv_step() {
+  if (difftest_step()) {
+    printf("Difftest error\n");
+  }
+}
diff --git a/src/test/vcs/UARTHelper.v b/src/test/vcs/UARTHelper.v
deleted file mode 100644
index c7a7b323ab946f8b760e5aa8f5e5560cb6768de9..0000000000000000000000000000000000000000
--- a/src/test/vcs/UARTHelper.v
+++ /dev/null
@@ -1,22 +0,0 @@
-import "DPI-C" function void uart_putchar
-(
-  input byte c
-);
-
-module UARTHelper(
-  input         clock,
-  input         reset,
-  input         putchar_valid,
-  input  [7:0]  putchar_ch,
-  input         getchar_valid,
-  output [7:0]  getchar_ch
-);
-
-always@(posedge clock) begin
-  if(putchar_valid)
-    uart_putchar(putchar_ch);
-end
-
-assign getchar_ch = 'h0;
-
-endmodule
diff --git a/src/test/vcs/common.c b/src/test/vcs/common.c
deleted file mode 100644
index a24e651307035dddbbc5970a1bf5293893a3a984..0000000000000000000000000000000000000000
--- a/src/test/vcs/common.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-
-void xs_assert(long long line) {
-  printf("Assertion failed at line %lld.\n", line);
-}
-
diff --git a/src/test/vcs/ram.c b/src/test/vcs/ram.c
deleted file mode 100644
index 42cd4726057563011da8e7b001f7e4e35aff1f71..0000000000000000000000000000000000000000
--- a/src/test/vcs/ram.c
+++ /dev/null
@@ -1,67 +0,0 @@
-#include <sys/mman.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-
-#define EMU_RAM_SIZE (256 * 1024 * 1024UL)
-
-static uint64_t *ram;
-static long img_size = 0;
-
-
-void init_ram() {
-  const char *img = "./ram.bin";
-  //assert(img != NULL);
-
-  printf("The image is %s\n", img);
-
-  // initialize memory using Linux mmap
-  printf("Using simulated %luMB RAM\n", EMU_RAM_SIZE / (1024 * 1024));
-  ram = (uint64_t *)mmap(NULL, EMU_RAM_SIZE, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
-  if (ram == (uint64_t *)MAP_FAILED) {
-    printf("Cound not mmap 0x%lx bytes\n", EMU_RAM_SIZE);
-    //assert(0);
-  }
-
-  FILE *fp = fopen(img, "rb");
-  if (fp == NULL) {
-    printf("Can not open '%s'\n", img);
-    //assert(0);
-  }
-
-  fseek(fp, 0, SEEK_END);
-  img_size = ftell(fp);
-  if (img_size > EMU_RAM_SIZE) {
-    img_size = EMU_RAM_SIZE;
-  }
-
-  fseek(fp, 0, SEEK_SET);
-  fread(ram, img_size, 1, fp);
-
-  fclose(fp);
-
-}
-
-void ram_finish() {
-  munmap(ram, EMU_RAM_SIZE);
-}
-
-
-uint64_t ram_read_helper(uint8_t en, uint64_t rIdx) {
-  if (en && rIdx >= EMU_RAM_SIZE / sizeof(uint64_t)) {
-    rIdx %= EMU_RAM_SIZE / sizeof(uint64_t);
-  }
-  uint64_t rdata = (en) ? ram[rIdx] : 0;
-  return rdata;
-}
-
-void ram_write_helper(uint64_t wIdx, uint64_t wdata, uint64_t wmask, uint8_t wen) {
-  if (wen) {
-    if (wIdx >= EMU_RAM_SIZE / sizeof(uint64_t)) {
-      printf("ERROR: ram wIdx = 0x%lx out of bound!\n", wIdx);
-      return;
-      //assert(wIdx < EMU_RAM_SIZE / sizeof(uint64_t));
-    }
-    ram[wIdx] = (ram[wIdx] & ~wmask) | (wdata & wmask);
-  }
-}
diff --git a/src/test/vcs/ram.v b/src/test/vcs/ram.v
deleted file mode 100644
index 21343624e47f57155a446df4f03a9617337385d2..0000000000000000000000000000000000000000
--- a/src/test/vcs/ram.v
+++ /dev/null
@@ -1,41 +0,0 @@
-import "DPI-C" function void ram_write_helper
-(
-  input  longint    wIdx,
-  input  longint    wdata,
-  input  longint    wmask,
-  input  bit        wen
-);
-
-import "DPI-C" function longint ram_read_helper
-(
-  input  bit        en,
-  input  longint    rIdx
-);
-
-import "DPI-C" function void init_ram
-(
-);
-
-module RAMHelper(
-  input         clk,
-  input         en,
-  input  [63:0] rIdx,
-  output [63:0] rdata,
-  input  [63:0] wIdx,
-  input  [63:0] wdata,
-  input  [63:0] wmask,
-  input         wen
-);
-
-  initial begin
-    init_ram();
-  end
-
-  assign rdata = ram_read_helper(en, rIdx);
-
-  always @(posedge clk) begin
-    ram_write_helper(wIdx, wdata, wmask, wen && en);
-  end
-
-endmodule
-
diff --git a/src/test/vcs/sdcard.c b/src/test/vcs/sdcard.c
deleted file mode 100644
index 441cd27a7a4e7f27c165759cd740583d5eb13be4..0000000000000000000000000000000000000000
--- a/src/test/vcs/sdcard.c
+++ /dev/null
@@ -1,28 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-
-FILE *fp = NULL;
-
-void sd_setaddr(uint32_t addr) {
-  fseek(fp, addr, SEEK_SET);
-  //printf("set addr to 0x%08x\n", addr);
-  //assert(0);
-}
-
-uint32_t sd_read(int ren) {
-  if (ren) {
-    uint32_t data;
-    fread(&data, 4, 1, fp);
-    //printf("read data = 0x%08x\n", *data);
-    return data;
-  }
-  return 0xdeadbeaf;
-}
-
-void init_sd(void) {
-  fp = fopen("/home/xyn/debian/debian.img", "r");
-  if(!fp) {
-    printf("[warning] sdcard img not found\n");
-  }
-}
diff --git a/src/test/vcs/uart.c b/src/test/vcs/uart.c
deleted file mode 100644
index fff9556e378af4af438ec393e0c74d82f4e04008..0000000000000000000000000000000000000000
--- a/src/test/vcs/uart.c
+++ /dev/null
@@ -1,9 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-
-void uart_putchar(char c)
-{
-  printf("%c", c);
-  fflush(stdout);
-}
\ No newline at end of file
diff --git a/src/test/vcs/xs_vcs_top.v b/src/test/vcs/xs_vcs_top.v
deleted file mode 100644
index bd52b390913c7b37885bf4d99cdcaba9428bf276..0000000000000000000000000000000000000000
--- a/src/test/vcs/xs_vcs_top.v
+++ /dev/null
@@ -1,450 +0,0 @@
- module xs_system_top();
-
-wire         clock;
-wire         reset;
-wire  [63:0] io_difftest_r_0;
-wire  [63:0] io_difftest_r_1;
-wire  [63:0] io_difftest_r_2;
-wire  [63:0] io_difftest_r_3;
-wire  [63:0] io_difftest_r_4;
-wire  [63:0] io_difftest_r_5;
-wire  [63:0] io_difftest_r_6;
-wire  [63:0] io_difftest_r_7;
-wire  [63:0] io_difftest_r_8;
-wire  [63:0] io_difftest_r_9;
-wire  [63:0] io_difftest_r_10;
-wire  [63:0] io_difftest_r_11;
-wire  [63:0] io_difftest_r_12;
-wire  [63:0] io_difftest_r_13;
-wire  [63:0] io_difftest_r_14;
-wire  [63:0] io_difftest_r_15;
-wire  [63:0] io_difftest_r_16;
-wire  [63:0] io_difftest_r_17;
-wire  [63:0] io_difftest_r_18;
-wire  [63:0] io_difftest_r_19;
-wire  [63:0] io_difftest_r_20;
-wire  [63:0] io_difftest_r_21;
-wire  [63:0] io_difftest_r_22;
-wire  [63:0] io_difftest_r_23;
-wire  [63:0] io_difftest_r_24;
-wire  [63:0] io_difftest_r_25;
-wire  [63:0] io_difftest_r_26;
-wire  [63:0] io_difftest_r_27;
-wire  [63:0] io_difftest_r_28;
-wire  [63:0] io_difftest_r_29;
-wire  [63:0] io_difftest_r_30;
-wire  [63:0] io_difftest_r_31;
-wire  [63:0] io_difftest_r_32;
-wire  [63:0] io_difftest_r_33;
-wire  [63:0] io_difftest_r_34;
-wire  [63:0] io_difftest_r_35;
-wire  [63:0] io_difftest_r_36;
-wire  [63:0] io_difftest_r_37;
-wire  [63:0] io_difftest_r_38;
-wire  [63:0] io_difftest_r_39;
-wire  [63:0] io_difftest_r_40;
-wire  [63:0] io_difftest_r_41;
-wire  [63:0] io_difftest_r_42;
-wire  [63:0] io_difftest_r_43;
-wire  [63:0] io_difftest_r_44;
-wire  [63:0] io_difftest_r_45;
-wire  [63:0] io_difftest_r_46;
-wire  [63:0] io_difftest_r_47;
-wire  [63:0] io_difftest_r_48;
-wire  [63:0] io_difftest_r_49;
-wire  [63:0] io_difftest_r_50;
-wire  [63:0] io_difftest_r_51;
-wire  [63:0] io_difftest_r_52;
-wire  [63:0] io_difftest_r_53;
-wire  [63:0] io_difftest_r_54;
-wire  [63:0] io_difftest_r_55;
-wire  [63:0] io_difftest_r_56;
-wire  [63:0] io_difftest_r_57;
-wire  [63:0] io_difftest_r_58;
-wire  [63:0] io_difftest_r_59;
-wire  [63:0] io_difftest_r_60;
-wire  [63:0] io_difftest_r_61;
-wire  [63:0] io_difftest_r_62;
-wire  [63:0] io_difftest_r_63;
-wire  [31:0] io_difftest_commit;
-wire  [63:0] io_difftest_thisPC;
-wire  [31:0] io_difftest_thisINST;
-wire  [31:0] io_difftest_skip;
-wire  [31:0] io_difftest_wen;
-wire  [63:0] io_difftest_wdata_0;
-wire  [63:0] io_difftest_wdata_1;
-wire  [63:0] io_difftest_wdata_2;
-wire  [63:0] io_difftest_wdata_3;
-wire  [63:0] io_difftest_wdata_4;
-wire  [63:0] io_difftest_wdata_5;
-wire  [31:0] io_difftest_wdst_0;
-wire  [31:0] io_difftest_wdst_1;
-wire  [31:0] io_difftest_wdst_2;
-wire  [31:0] io_difftest_wdst_3;
-wire  [31:0] io_difftest_wdst_4;
-wire  [31:0] io_difftest_wdst_5;
-wire  [63:0] io_difftest_wpc_0;
-wire  [63:0] io_difftest_wpc_1;
-wire  [63:0] io_difftest_wpc_2;
-wire  [63:0] io_difftest_wpc_3;
-wire  [63:0] io_difftest_wpc_4;
-wire  [63:0] io_difftest_wpc_5;
-wire  [31:0] io_difftest_isRVC;
-wire  [63:0] io_difftest_intrNO;
-wire  [63:0] io_difftest_cause;
-wire  [1:0]  io_difftest_priviledgeMode;
-wire  [63:0] io_difftest_mstatus;
-wire  [63:0] io_difftest_sstatus;
-wire  [63:0] io_difftest_mepc;
-wire  [63:0] io_difftest_sepc;
-wire  [63:0] io_difftest_mtval;
-wire  [63:0] io_difftest_stval;
-wire  [63:0] io_difftest_mtvec;
-wire  [63:0] io_difftest_stvec;
-wire  [63:0] io_difftest_mcause;
-wire  [63:0] io_difftest_scause;
-wire  [63:0] io_difftest_satp;
-wire  [63:0] io_difftest_mip;
-wire  [63:0] io_difftest_mie;
-wire  [63:0] io_difftest_mscratch;
-wire  [63:0] io_difftest_sscratch;
-wire  [63:0] io_difftest_mideleg;
-wire  [63:0] io_difftest_medeleg;
-wire         io_difftest_scFailed;
-wire  [1:0]  io_difftest_storeCommit;
-wire  [63:0] io_difftest_storeAddr_0;
-wire  [63:0] io_difftest_storeAddr_1;
-wire  [63:0] io_difftest_storeData_0;
-wire  [63:0] io_difftest_storeData_1;
-wire  [7:0]  io_difftest_storeMask_0;
-wire  [7:0]  io_difftest_storeMask_1;
-wire         io_difftest_sbufferResp;
-wire  [63:0] io_difftest_sbufferAddr;
-wire  [7:0]  io_difftest_sbufferData_0;
-wire  [7:0]  io_difftest_sbufferData_1;
-wire  [7:0]  io_difftest_sbufferData_2;
-wire  [7:0]  io_difftest_sbufferData_3;
-wire  [7:0]  io_difftest_sbufferData_4;
-wire  [7:0]  io_difftest_sbufferData_5;
-wire  [7:0]  io_difftest_sbufferData_6;
-wire  [7:0]  io_difftest_sbufferData_7;
-wire  [7:0]  io_difftest_sbufferData_8;
-wire  [7:0]  io_difftest_sbufferData_9;
-wire  [7:0]  io_difftest_sbufferData_10;
-wire  [7:0]  io_difftest_sbufferData_11;
-wire  [7:0]  io_difftest_sbufferData_12;
-wire  [7:0]  io_difftest_sbufferData_13;
-wire  [7:0]  io_difftest_sbufferData_14;
-wire  [7:0]  io_difftest_sbufferData_15;
-wire  [7:0]  io_difftest_sbufferData_16;
-wire  [7:0]  io_difftest_sbufferData_17;
-wire  [7:0]  io_difftest_sbufferData_18;
-wire  [7:0]  io_difftest_sbufferData_19;
-wire  [7:0]  io_difftest_sbufferData_20;
-wire  [7:0]  io_difftest_sbufferData_21;
-wire  [7:0]  io_difftest_sbufferData_22;
-wire  [7:0]  io_difftest_sbufferData_23;
-wire  [7:0]  io_difftest_sbufferData_24;
-wire  [7:0]  io_difftest_sbufferData_25;
-wire  [7:0]  io_difftest_sbufferData_26;
-wire  [7:0]  io_difftest_sbufferData_27;
-wire  [7:0]  io_difftest_sbufferData_28;
-wire  [7:0]  io_difftest_sbufferData_29;
-wire  [7:0]  io_difftest_sbufferData_30;
-wire  [7:0]  io_difftest_sbufferData_31;
-wire  [7:0]  io_difftest_sbufferData_32;
-wire  [7:0]  io_difftest_sbufferData_33;
-wire  [7:0]  io_difftest_sbufferData_34;
-wire  [7:0]  io_difftest_sbufferData_35;
-wire  [7:0]  io_difftest_sbufferData_36;
-wire  [7:0]  io_difftest_sbufferData_37;
-wire  [7:0]  io_difftest_sbufferData_38;
-wire  [7:0]  io_difftest_sbufferData_39;
-wire  [7:0]  io_difftest_sbufferData_40;
-wire  [7:0]  io_difftest_sbufferData_41;
-wire  [7:0]  io_difftest_sbufferData_42;
-wire  [7:0]  io_difftest_sbufferData_43;
-wire  [7:0]  io_difftest_sbufferData_44;
-wire  [7:0]  io_difftest_sbufferData_45;
-wire  [7:0]  io_difftest_sbufferData_46;
-wire  [7:0]  io_difftest_sbufferData_47;
-wire  [7:0]  io_difftest_sbufferData_48;
-wire  [7:0]  io_difftest_sbufferData_49;
-wire  [7:0]  io_difftest_sbufferData_50;
-wire  [7:0]  io_difftest_sbufferData_51;
-wire  [7:0]  io_difftest_sbufferData_52;
-wire  [7:0]  io_difftest_sbufferData_53;
-wire  [7:0]  io_difftest_sbufferData_54;
-wire  [7:0]  io_difftest_sbufferData_55;
-wire  [7:0]  io_difftest_sbufferData_56;
-wire  [7:0]  io_difftest_sbufferData_57;
-wire  [7:0]  io_difftest_sbufferData_58;
-wire  [7:0]  io_difftest_sbufferData_59;
-wire  [7:0]  io_difftest_sbufferData_60;
-wire  [7:0]  io_difftest_sbufferData_61;
-wire  [7:0]  io_difftest_sbufferData_62;
-wire  [7:0]  io_difftest_sbufferData_63;
-wire  [63:0] io_difftest_sbufferMask;
-wire  [63:0] io_logCtrl_log_begin;
-wire  [63:0] io_logCtrl_log_end;
-wire  [63:0] io_logCtrl_log_level;
-wire         io_trap_valid;
-wire  [2:0]  io_trap_code;
-wire  [38:0] io_trap_pc;
-wire  [63:0] io_trap_cycleCnt;
-wire  [63:0] io_trap_instrCnt;
-wire         io_uart_out_valid;
-wire  [7:0]  io_uart_out_ch;
-wire         io_uart_in_valid;
-wire  [7:0]  io_uart_in_ch;
-
-assign io_logCtrl_log_begin = 'h0;
-assign io_logCtrl_log_end   = 'h0;
-assign io_logCtrl_log_level = 'h0;
-
-rcg rcg0
-(
-  .clock(clock),
-  .reset(reset)
-);
-
-UARTHelper UARTHelper0
-(
-  .clock(clock),
-  .reset(reset),
-  .putchar_valid(io_uart_out_valid),
-  .putchar_ch(io_uart_out_ch),
-  .getchar_valid(io_uart_in_valid),
-  .getchar_ch(io_uart_in_ch)
-);
-
-XSSimSoC XSSimSoC0
-(
-  .clock(clock),
-  .reset(reset),
-  .io_difftest_r_0(io_difftest_r_0),
-  .io_difftest_r_1(io_difftest_r_1),
-  .io_difftest_r_2(io_difftest_r_2),
-  .io_difftest_r_3(io_difftest_r_3),
-  .io_difftest_r_4(io_difftest_r_4),
-  .io_difftest_r_5(io_difftest_r_5),
-  .io_difftest_r_6(io_difftest_r_6),
-  .io_difftest_r_7(io_difftest_r_7),
-  .io_difftest_r_8(io_difftest_r_8),
-  .io_difftest_r_9(io_difftest_r_9),
-  .io_difftest_r_10(io_difftest_r_10),
-  .io_difftest_r_11(io_difftest_r_11),
-  .io_difftest_r_12(io_difftest_r_12),
-  .io_difftest_r_13(io_difftest_r_13),
-  .io_difftest_r_14(io_difftest_r_14),
-  .io_difftest_r_15(io_difftest_r_15),
-  .io_difftest_r_16(io_difftest_r_16),
-  .io_difftest_r_17(io_difftest_r_17),
-  .io_difftest_r_18(io_difftest_r_18),
-  .io_difftest_r_19(io_difftest_r_19),
-  .io_difftest_r_20(io_difftest_r_20),
-  .io_difftest_r_21(io_difftest_r_21),
-  .io_difftest_r_22(io_difftest_r_22),
-  .io_difftest_r_23(io_difftest_r_23),
-  .io_difftest_r_24(io_difftest_r_24),
-  .io_difftest_r_25(io_difftest_r_25),
-  .io_difftest_r_26(io_difftest_r_26),
-  .io_difftest_r_27(io_difftest_r_27),
-  .io_difftest_r_28(io_difftest_r_28),
-  .io_difftest_r_29(io_difftest_r_29),
-  .io_difftest_r_30(io_difftest_r_30),
-  .io_difftest_r_31(io_difftest_r_31),
-  .io_difftest_r_32(io_difftest_r_32),
-  .io_difftest_r_33(io_difftest_r_33),
-  .io_difftest_r_34(io_difftest_r_34),
-  .io_difftest_r_35(io_difftest_r_35),
-  .io_difftest_r_36(io_difftest_r_36),
-  .io_difftest_r_37(io_difftest_r_37),
-  .io_difftest_r_38(io_difftest_r_38),
-  .io_difftest_r_39(io_difftest_r_39),
-  .io_difftest_r_40(io_difftest_r_40),
-  .io_difftest_r_41(io_difftest_r_41),
-  .io_difftest_r_42(io_difftest_r_42),
-  .io_difftest_r_43(io_difftest_r_43),
-  .io_difftest_r_44(io_difftest_r_44),
-  .io_difftest_r_45(io_difftest_r_45),
-  .io_difftest_r_46(io_difftest_r_46),
-  .io_difftest_r_47(io_difftest_r_47),
-  .io_difftest_r_48(io_difftest_r_48),
-  .io_difftest_r_49(io_difftest_r_49),
-  .io_difftest_r_50(io_difftest_r_50),
-  .io_difftest_r_51(io_difftest_r_51),
-  .io_difftest_r_52(io_difftest_r_52),
-  .io_difftest_r_53(io_difftest_r_53),
-  .io_difftest_r_54(io_difftest_r_54),
-  .io_difftest_r_55(io_difftest_r_55),
-  .io_difftest_r_56(io_difftest_r_56),
-  .io_difftest_r_57(io_difftest_r_57),
-  .io_difftest_r_58(io_difftest_r_58),
-  .io_difftest_r_59(io_difftest_r_59),
-  .io_difftest_r_60(io_difftest_r_60),
-  .io_difftest_r_61(io_difftest_r_61),
-  .io_difftest_r_62(io_difftest_r_62),
-  .io_difftest_r_63(io_difftest_r_63),
-  .io_difftest_commit(io_difftest_commit),
-  .io_difftest_thisPC(io_difftest_thisPC),
-  .io_difftest_thisINST(io_difftest_thisINST),
-  .io_difftest_skip(io_difftest_skip),
-  .io_difftest_wen(io_difftest_wen),
-  .io_difftest_wdata_0(io_difftest_wdata_0),
-  .io_difftest_wdata_1(io_difftest_wdata_1),
-  .io_difftest_wdata_2(io_difftest_wdata_2),
-  .io_difftest_wdata_3(io_difftest_wdata_3),
-  .io_difftest_wdata_4(io_difftest_wdata_4),
-  .io_difftest_wdata_5(io_difftest_wdata_5),
-  .io_difftest_wdst_0(io_difftest_wdst_0),
-  .io_difftest_wdst_1(io_difftest_wdst_1),
-  .io_difftest_wdst_2(io_difftest_wdst_2),
-  .io_difftest_wdst_3(io_difftest_wdst_3),
-  .io_difftest_wdst_4(io_difftest_wdst_4),
-  .io_difftest_wdst_5(io_difftest_wdst_5),
-  .io_difftest_wpc_0(io_difftest_wpc_0),
-  .io_difftest_wpc_1(io_difftest_wpc_1),
-  .io_difftest_wpc_2(io_difftest_wpc_2),
-  .io_difftest_wpc_3(io_difftest_wpc_3),
-  .io_difftest_wpc_4(io_difftest_wpc_4),
-  .io_difftest_wpc_5(io_difftest_wpc_5),
-  .io_difftest_isRVC(io_difftest_isRVC),
-  .io_difftest_intrNO(io_difftest_intrNO),
-  .io_difftest_cause(io_difftest_cause),
-  .io_difftest_priviledgeMode(io_difftest_priviledgeMode),
-  .io_difftest_mstatus(io_difftest_mstatus),
-  .io_difftest_sstatus(io_difftest_sstatus),
-  .io_difftest_mepc(io_difftest_mepc),
-  .io_difftest_sepc(io_difftest_sepc),
-  .io_difftest_mtval(io_difftest_mtval),
-  .io_difftest_stval(io_difftest_stval),
-  .io_difftest_mtvec(io_difftest_mtvec),
-  .io_difftest_stvec(io_difftest_stvec),
-  .io_difftest_mcause(io_difftest_mcause),
-  .io_difftest_scause(io_difftest_scause),
-  .io_difftest_satp(io_difftest_satp),
-  .io_difftest_mip(io_difftest_mip),
-  .io_difftest_mie(io_difftest_mie),
-  .io_difftest_mscratch(io_difftest_mscratch),
-  .io_difftest_sscratch(io_difftest_sscratch),
-  .io_difftest_mideleg(io_difftest_mideleg),
-  .io_difftest_medeleg(io_difftest_medeleg),
-  .io_difftest_scFailed(io_difftest_scFailed),
-  .io_difftest_storeCommit(io_difftest_storeCommit),
-  .io_difftest_storeAddr_0(io_difftest_storeAddr_0),
-  .io_difftest_storeAddr_1(io_difftest_storeAddr_1),
-  .io_difftest_storeData_0(io_difftest_storeData_0),
-  .io_difftest_storeData_1(io_difftest_storeData_1),
-  .io_difftest_storeMask_0(io_difftest_storeMask_0),
-  .io_difftest_storeMask_1(io_difftest_storeMask_1),
-  .io_difftest_sbufferResp(io_difftest_sbufferResp),
-  .io_difftest_sbufferAddr(io_difftest_sbufferAddr),
-  .io_difftest_sbufferData_0(io_difftest_sbufferData_0),
-  .io_difftest_sbufferData_1(io_difftest_sbufferData_1),
-  .io_difftest_sbufferData_2(io_difftest_sbufferData_2),
-  .io_difftest_sbufferData_3(io_difftest_sbufferData_3),
-  .io_difftest_sbufferData_4(io_difftest_sbufferData_4),
-  .io_difftest_sbufferData_5(io_difftest_sbufferData_5),
-  .io_difftest_sbufferData_6(io_difftest_sbufferData_6),
-  .io_difftest_sbufferData_7(io_difftest_sbufferData_7),
-  .io_difftest_sbufferData_8(io_difftest_sbufferData_8),
-  .io_difftest_sbufferData_9(io_difftest_sbufferData_9),
-  .io_difftest_sbufferData_10(io_difftest_sbufferData_10),
-  .io_difftest_sbufferData_11(io_difftest_sbufferData_11),
-  .io_difftest_sbufferData_12(io_difftest_sbufferData_12),
-  .io_difftest_sbufferData_13(io_difftest_sbufferData_13),
-  .io_difftest_sbufferData_14(io_difftest_sbufferData_14),
-  .io_difftest_sbufferData_15(io_difftest_sbufferData_15),
-  .io_difftest_sbufferData_16(io_difftest_sbufferData_16),
-  .io_difftest_sbufferData_17(io_difftest_sbufferData_17),
-  .io_difftest_sbufferData_18(io_difftest_sbufferData_18),
-  .io_difftest_sbufferData_19(io_difftest_sbufferData_19),
-  .io_difftest_sbufferData_20(io_difftest_sbufferData_20),
-  .io_difftest_sbufferData_21(io_difftest_sbufferData_21),
-  .io_difftest_sbufferData_22(io_difftest_sbufferData_22),
-  .io_difftest_sbufferData_23(io_difftest_sbufferData_23),
-  .io_difftest_sbufferData_24(io_difftest_sbufferData_24),
-  .io_difftest_sbufferData_25(io_difftest_sbufferData_25),
-  .io_difftest_sbufferData_26(io_difftest_sbufferData_26),
-  .io_difftest_sbufferData_27(io_difftest_sbufferData_27),
-  .io_difftest_sbufferData_28(io_difftest_sbufferData_28),
-  .io_difftest_sbufferData_29(io_difftest_sbufferData_29),
-  .io_difftest_sbufferData_30(io_difftest_sbufferData_30),
-  .io_difftest_sbufferData_31(io_difftest_sbufferData_31),
-  .io_difftest_sbufferData_32(io_difftest_sbufferData_32),
-  .io_difftest_sbufferData_33(io_difftest_sbufferData_33),
-  .io_difftest_sbufferData_34(io_difftest_sbufferData_34),
-  .io_difftest_sbufferData_35(io_difftest_sbufferData_35),
-  .io_difftest_sbufferData_36(io_difftest_sbufferData_36),
-  .io_difftest_sbufferData_37(io_difftest_sbufferData_37),
-  .io_difftest_sbufferData_38(io_difftest_sbufferData_38),
-  .io_difftest_sbufferData_39(io_difftest_sbufferData_39),
-  .io_difftest_sbufferData_40(io_difftest_sbufferData_40),
-  .io_difftest_sbufferData_41(io_difftest_sbufferData_41),
-  .io_difftest_sbufferData_42(io_difftest_sbufferData_42),
-  .io_difftest_sbufferData_43(io_difftest_sbufferData_43),
-  .io_difftest_sbufferData_44(io_difftest_sbufferData_44),
-  .io_difftest_sbufferData_45(io_difftest_sbufferData_45),
-  .io_difftest_sbufferData_46(io_difftest_sbufferData_46),
-  .io_difftest_sbufferData_47(io_difftest_sbufferData_47),
-  .io_difftest_sbufferData_48(io_difftest_sbufferData_48),
-  .io_difftest_sbufferData_49(io_difftest_sbufferData_49),
-  .io_difftest_sbufferData_50(io_difftest_sbufferData_50),
-  .io_difftest_sbufferData_51(io_difftest_sbufferData_51),
-  .io_difftest_sbufferData_52(io_difftest_sbufferData_52),
-  .io_difftest_sbufferData_53(io_difftest_sbufferData_53),
-  .io_difftest_sbufferData_54(io_difftest_sbufferData_54),
-  .io_difftest_sbufferData_55(io_difftest_sbufferData_55),
-  .io_difftest_sbufferData_56(io_difftest_sbufferData_56),
-  .io_difftest_sbufferData_57(io_difftest_sbufferData_57),
-  .io_difftest_sbufferData_58(io_difftest_sbufferData_58),
-  .io_difftest_sbufferData_59(io_difftest_sbufferData_59),
-  .io_difftest_sbufferData_60(io_difftest_sbufferData_60),
-  .io_difftest_sbufferData_61(io_difftest_sbufferData_61),
-  .io_difftest_sbufferData_62(io_difftest_sbufferData_62),
-  .io_difftest_sbufferData_63(io_difftest_sbufferData_63),
-  .io_difftest_sbufferMask(io_difftest_sbufferMask),
-  .io_logCtrl_log_begin(io_logCtrl_log_begin),
-  .io_logCtrl_log_end(io_logCtrl_log_end),
-  .io_logCtrl_log_level(io_logCtrl_log_level),
-  .io_trap_valid(io_trap_valid),
-  .io_trap_code(io_trap_code),
-  .io_trap_pc(io_trap_pc),
-  .io_trap_cycleCnt(io_trap_cycleCnt),
-  .io_trap_instrCnt(io_trap_instrCnt),
-  .io_uart_out_valid(io_uart_out_valid),
-  .io_uart_out_ch(io_uart_out_ch),
-  .io_uart_in_valid(io_uart_in_valid),
-  .io_uart_in_ch(io_uart_in_ch)
-);
-
-endmodule
-
-module rcg
-(
-  clock,
-  reset
-);
-
-output clock;
-output reset;
-
-reg clock;
-reg reset;
-
-initial begin
-  clock <= 0;
-  reset <= 1;
-  #500 reset <= 0;
-end
-
-always begin
-  #1 clock <= ~clock;
-end
-
-initial begin
-  $vcdpluson;
-end
-
-endmodule
diff --git a/src/test/vsrc/assert.v b/src/test/vsrc/assert.v
deleted file mode 100644
index 7d4f6f224fd53d3176c4620f165c85761bed577a..0000000000000000000000000000000000000000
--- a/src/test/vsrc/assert.v
+++ /dev/null
@@ -1,4 +0,0 @@
-import "DPI-C" function void xs_assert
-(
-  input  longint    line
-);
diff --git a/src/test/vcs/assert.v b/src/test/vsrc/common/assert.v
similarity index 100%
rename from src/test/vcs/assert.v
rename to src/test/vsrc/common/assert.v
diff --git a/src/test/vsrc/difftest.v b/src/test/vsrc/common/difftest.v
similarity index 99%
rename from src/test/vsrc/difftest.v
rename to src/test/vsrc/common/difftest.v
index eebd23b37ed24993eddc41056ed6ed6f5b84ec07..8533c0a44a75fd3da86b12fcecacc3a14bf6b9f8 100644
--- a/src/test/vsrc/difftest.v
+++ b/src/test/vsrc/common/difftest.v
@@ -569,6 +569,6 @@ endmodule
   input [63:0] ptwData_3
 );
   `DIFFTEST_MOD_DPIC_CALL_BEGIN_WITH_EN(ptwResp, PtwEvent) (
-    coreid, ptwResp, ptwData_0, ptwData_1, ptwData_2, ptwData_3
+    coreid, ptwResp, ptwAddr, ptwData_0, ptwData_1, ptwData_2, ptwData_3
   ) `DIFFTEST_MOD_DPIC_CALL_END_WITH_EN(PtwEvent)
 endmodule
diff --git a/src/test/vsrc/ram.v b/src/test/vsrc/common/ram.v
similarity index 100%
rename from src/test/vsrc/ram.v
rename to src/test/vsrc/common/ram.v
diff --git a/src/test/vsrc/ref.v b/src/test/vsrc/common/ref.v
similarity index 100%
rename from src/test/vsrc/ref.v
rename to src/test/vsrc/common/ref.v
diff --git a/src/test/vsrc/vcs/top.v b/src/test/vsrc/vcs/top.v
new file mode 100644
index 0000000000000000000000000000000000000000..dda372a61019d7788732626c2e292ee46557fdae
--- /dev/null
+++ b/src/test/vsrc/vcs/top.v
@@ -0,0 +1,72 @@
+import "DPI-C" function void simv_init();
+import "DPI-C" function void simv_step();
+
+module tb_top();
+
+reg         clock;
+reg         reset;
+wire [63:0] io_logCtrl_log_begin;
+wire [63:0] io_logCtrl_log_end;
+wire [63:0] io_logCtrl_log_level;
+wire        io_perfInfo_clean;
+wire        io_perfInfo_dump;
+wire        io_uart_out_valid;
+wire [ 7:0] io_uart_out_ch;
+wire        io_uart_in_valid;
+wire [ 7:0] io_uart_in_ch;
+
+initial begin
+  clock = 0;
+  reset = 1;
+  #100 reset = 0;
+  if ($test$plusargs("dump-wave")) begin
+    $vcdplusfile("simv.vpd");
+    $vcdpluson;
+  end
+end
+always #1 clock <= ~clock;
+
+SimTop sim(
+  .clock(clock),
+  .reset(reset),
+  .io_logCtrl_log_begin(io_logCtrl_log_begin),
+  .io_logCtrl_log_end(io_logCtrl_log_end),
+  .io_logCtrl_log_level(io_logCtrl_log_level),
+  .io_perfInfo_clean(io_perfInfo_clean),
+  .io_perfInfo_dump(io_perfInfo_dump),
+  .io_uart_out_valid(io_uart_out_valid),
+  .io_uart_out_ch(io_uart_out_ch),
+  .io_uart_in_valid(io_uart_in_valid),
+  .io_uart_in_ch(io_uart_in_ch)
+);
+
+assign io_logCtrl_log_begin = 0;
+assign io_logCtrl_log_end = 0;
+assign io_logCtrl_log_level = 0;
+assign io_perfInfo_clean = 0;
+assign io_perfInfo_dump = 0;
+assign io_uart_in_ch = 8'hff;
+
+always @(posedge clock) begin
+  if (!reset && io_uart_out_valid) begin
+    $write("%c", io_uart_out_ch);
+  end
+end
+
+reg has_init;
+always @(posedge clock) begin
+  if (reset) begin
+    has_init <= 1'b0;
+  end
+  else if (!has_init) begin
+    simv_init();
+    has_init <= 1'b1;
+  end
+
+  if (!reset && has_init) begin
+    simv_step();
+  end
+end
+
+endmodule
+
diff --git a/vcs.mk b/vcs.mk
new file mode 100644
index 0000000000000000000000000000000000000000..54b34655a8e360f4adc09bd4f612f0136cff2fcc
--- /dev/null
+++ b/vcs.mk
@@ -0,0 +1,32 @@
+VCS_TARGET = simv
+
+VCS_CSRC_DIR = $(abspath ./src/test/csrc/vcs)
+VCS_CXXFILES = $(SIM_CXXFILES) $(DIFFTEST_CXXFILES) $(shell find $(VCS_CSRC_DIR) -name "*.cpp")
+VCS_CXXFLAGS += -std=c++11 -static -Wall -I$(VCS_CSRC_DIR) -I$(SIM_CSRC_DIR) -I$(DIFFTEST_CSRC_DIR)
+VCS_LDFLAGS  += -lpthread -lSDL2 -ldl -lz
+
+VCS_VSRC_DIR = $(abspath ./src/test/vsrc/vcs)
+VCS_VFILES   = $(SIM_VSRC) $(shell find $(VCS_VSRC_DIR) -name "*.v")
+
+VCS_SEARCH_DIR = $(abspath ./build)
+VCS_BUILD_DIR  = $(abspath ./build/simv-compile)
+
+VCS_FLAGS += -full64 +v2k -timescale=1ns/1ns -sverilog -debug_access+all +lint=TFIPC-L
+# randomize all undefined signals (instead of using X)
+VCS_FLAGS += +define+RANDOMIZE_GARBAGE_ASSIGN +define+RANDOMIZE_INVALID_ASSIGN
+VCS_FLAGS += +define+RANDOMIZE_MEM_INIT +define+RANDOMIZE_DELAY=0 +define+RANDOMIZE_REG_INIT
+# SRAM lib defines
+VCS_FLAGS += +define+UNIT_DELAY +define+no_warning
+# C++ flags
+VCS_FLAGS += -CFLAGS "$(VCS_CXXFLAGS)" -LDFLAGS "$(VCS_LDFLAGS)"
+# search build for other missing verilog files
+VCS_FLAGS += -y $(VCS_SEARCH_DIR) +libext+.v
+# build files put into $(VCS_BUILD_DIR)
+VCS_FLAGS += -Mdir=$(VCS_BUILD_DIR)
+
+$(VCS_TARGET): $(SIM_TOP_V) $(VCS_CXXFILES) $(VCS_VFILES)
+	vcs $(VCS_FLAGS) $(SIM_TOP_V) $(VCS_CXXFILES) $(VCS_VFILES)
+
+vcs-clean:
+	rm -rf simv csrc DVEfiles simv.daidir stack.info.* ucli.key $(VCS_BUILD_DIR)
+
diff --git a/Makefile.emu b/verilator.mk
similarity index 100%
rename from Makefile.emu
rename to verilator.mk