diff --git a/driver/Makefile b/driver/Makefile
index 215a0362..58de93a2 100644
--- a/driver/Makefile
+++ b/driver/Makefile
@@ -1,4 +1,4 @@
-all: stub rtlsim simx
+all: stub rtlsim simx opae
 
 stub:
 	$(MAKE) -C stub
diff --git a/driver/opae/Makefile b/driver/opae/Makefile
index 9946470f..a2ebdd05 100644
--- a/driver/opae/Makefile
+++ b/driver/opae/Makefile
@@ -1,9 +1,10 @@
+OPAE_HOME ?= /tools/opae/1.4.0
 
 CXXFLAGS += -std=c++11 -O0 -g -Wall -Wextra -pedantic -Wfatal-errors
 
-CXXFLAGS += -I../include -I/tools/opae/1.4.0/include  -I../../hw
+CXXFLAGS += -I../include -I$(OPAE_HOME)/include  -I../../hw
 
-LDFLAGS += -L/tools/opae/1.4.0/lib
+LDFLAGS += -L$(OPAE_HOME)/lib
 
 # stack execution protection
 LDFLAGS +=-z noexecstack
@@ -23,49 +24,60 @@ CXXFLAGS += -DDUMP_PERF_STATS
 # Enable scope analyzer
 #CXXFLAGS += -DSCOPE
 
-LDFLAGS += -luuid
-
 LDFLAGS += -shared
 
-FPGA_LIBS += -lopae-c
+FPGA_LIBS += -luuid -lopae-c
 
-ASE_LIBS += -lopae-c-ase
+ASE_LIBS += -luuid -lopae-c-ase
+
+VLSIM_LIBS += -lopae-c-vlsim
 
 LIB_DIR=../lib
 
 ASE_DIR = ase
 
+VLSIM_DIR = vlsim
+
 PROJECT = libvortex.so
 
 PROJECT_ASE = $(ASE_DIR)/libvortex.so
 
+PROJECT_VLSIM = $(VLSIM_DIR)/libvortex.so
+
 AFU_JSON_INFO = vortex_afu.h
 
-SRCS = vortex.cpp scope.cpp ../common/vx_utils.cpp
+SRCS = vortex.cpp vx_scope.cpp ../common/vx_utils.cpp
 
-all: $(PROJECT) $(PROJECT_ASE)
+all: vlsim
 
 # AFU info from JSON file, including AFU UUID
-$(AFU_JSON_INFO): ../../hw/opae/vortex_afu.json
+json: ../../hw/opae/vortex_afu.json
 	afu_json_mgr json-info --afu-json=$^ --c-hdr=$@
 
-$(PROJECT): $(SRCS)
-	$(CXX) $(CXXFLAGS) $^ $(LDFLAGS) $(FPGA_LIBS) -o $@
+fpga: $(SRCS)
+	$(CXX) $(CXXFLAGS) $^ $(LDFLAGS) $(FPGA_LIBS) -o $(PROJECT)
 
-$(PROJECT_ASE): $(SRCS) $(ASE_DIR)
-	$(CXX) $(CXXFLAGS) -DUSE_ASE $(SRCS) $(LDFLAGS) $(ASE_LIBS) -o $@
+ase: $(SRCS) $(ASE_DIR)
+	$(CXX) $(CXXFLAGS) -DUSE_ASE $(SRCS) $(LDFLAGS) $(ASE_LIBS) -o $(PROJECT_ASE)
 
-vortex.o: vortex.cpp $(AFU_JSON_INFO)
+vlsim: $(SRCS) opae-vlsim
+	$(CXX) $(CXXFLAGS) -L./vlsim -DUSE_VLSIM $(SRCS) $(LDFLAGS) $(VLSIM_LIBS) -o $(PROJECT_VLSIM)
+
+opae-vlsim:
+	$(MAKE) -C vlsim
+
+vortex.o: vortex.cpp
 	$(CXX) $(CXXFLAGS) -c vortex.cpp -o $@
 
 $(ASE_DIR):
 	mkdir -p ase
 
-.depend: $(SRCS) $(AFU_JSON_INFO)
+.depend: $(SRCS)
 	$(CXX) $(CXXFLAGS) -MM $(SRCS) > .depend;
 
 clean:
-	rm -rf $(PROJECT) $(PROJECT_ASE) $(AFU_JSON_INFO) *.o .depend 
+	rm -rf $(PROJECT) $(PROJECT_ASE) $(PROJECT_VLSIM) *.o .depend
+	$(MAKE) -C vlsim clean	
 
 ifneq ($(MAKECMDGOALS),clean)
     -include .depend
diff --git a/driver/opae/vlsim/Makefile b/driver/opae/vlsim/Makefile
new file mode 100644
index 00000000..a30b6eda
--- /dev/null
+++ b/driver/opae/vlsim/Makefile
@@ -0,0 +1,78 @@
+#CFLAGS += -std=c++11 -O2 -DNDEBUG -Wall -Wextra -Wfatal-errors
+CFLAGS += -std=c++11 -g -O0 -Wall -Wextra -Wfatal-errors
+
+CFLAGS += -I../../../../hw
+
+# control RTL debug print states
+DBG_PRINT_FLAGS += -DDBG_PRINT_CORE_ICACHE
+DBG_PRINT_FLAGS += -DDBG_PRINT_CORE_DCACHE
+DBG_PRINT_FLAGS += -DDBG_PRINT_CACHE_BANK 
+DBG_PRINT_FLAGS += -DDBG_PRINT_CACHE_SNP 
+DBG_PRINT_FLAGS += -DDBG_PRINT_CACHE_MSRQ
+DBG_PRINT_FLAGS += -DDBG_PRINT_DRAM      
+DBG_PRINT_FLAGS += -DDBG_PRINT_PIPELINE  
+DBG_PRINT_FLAGS += -DDBG_PRINT_OPAE
+
+DBG_FLAGS += $(DBG_PRINT_FLAGS)
+DBG_FLAGS += -DDBG_CORE_REQ_INFO
+
+#CONFIGS += -DNUM_CLUSTERS=2 -DNUM_CORES=4 -DL2_ENABLE=1
+#CONFIGS += -DNUM_CLUSTERS=1 -DNUM_CORES=4 -DL2_ENABLE=1
+#CONFIGS += -DNUM_CLUSTERS=1 -DNUM_CORES=2 -DL2_ENABLE=0
+CONFIGS += -DNUM_CLUSTERS=1 -DNUM_CORES=1
+
+#DEBUG=1
+
+CFLAGS += -fPIC
+
+CFLAGS += -DUSE_RTLSIM $(CONFIGS)
+
+CFLAGS += -DDUMP_PERF_STATS
+
+LDFLAGS += -shared -pthread
+# LDFLAGS += -dynamiclib -pthread
+
+TOP = vortex_afu_shim
+
+RTL_DIR = ../../../hw/rtl
+
+SRCS = fpga.cpp opae_sim.cpp
+SRCS += $(RTL_DIR)/fp_cores/svdpi/float_dpi.cpp
+
+FPU_INCLUDE = -I$(RTL_DIR)/fp_cores -I$(RTL_DIR)/fp_cores/svdpi -I$(RTL_DIR)/fp_cores/fpnew/src/common_cells/include -I$(RTL_DIR)/fp_cores/fpnew/src/common_cells/src -I$(RTL_DIR)/fp_cores/fpnew/src/fpu_div_sqrt_mvp/hdl -I$(RTL_DIR)/fp_cores/fpnew/src 
+RTL_INCLUDE = -I$(RTL_DIR) -I$(RTL_DIR)/libs -I$(RTL_DIR)/interfaces -I$(RTL_DIR)/cache $(FPU_INCLUDE)
+
+VL_FLAGS += --language 1800-2009 --assert -Wall -Wpedantic $(CONFIGS)
+VL_FLAGS += -Wno-DECLFILENAME
+VL_FLAGS += --x-initial unique --x-assign unique
+VL_FLAGS += verilator.vlt
+
+# Enable Verilator multithreaded simulation
+#THREADS ?= $(shell python3 -c 'import multiprocessing as mp; print(max(1, mp.cpu_count() // 2))')
+#VL_FLAGS += --threads $(THREADS)
+
+# Debugigng
+ifdef DEBUG
+	VL_FLAGS += -DVCD_OUTPUT --assert --trace $(DBG_FLAGS)
+	CFLAGS   += -DVCD_OUTPUT $(DBG_FLAGS)
+else    
+	VL_FLAGS += -DNDEBUG
+	CFLAGS   += -DNDEBUG
+endif
+
+VL_FLAGS += -DNOPAE
+CFLAGS += -DNOPAE
+VL_FLAGS += -DSCOPE
+CFLAGS += -DSCOPE
+RTL_INCLUDE += -I../../../hw/opae  -I../../../hw/opae/ccip
+
+PROJECT = libopae-c-vlsim.so
+
+all: $(PROJECT)
+	
+$(PROJECT): $(SRCS)
+	verilator --exe --cc $(TOP) --top-module $(TOP) $(RTL_INCLUDE) $(VL_FLAGS) $(SRCS) -CFLAGS '$(CFLAGS)' -LDFLAGS '$(LDFLAGS)' -o ../$(PROJECT)
+	make -j -C obj_dir -f V$(TOP).mk
+
+clean:
+	rm -rf $(PROJECT) obj_dir
diff --git a/driver/opae/vlsim/fpga.cpp b/driver/opae/vlsim/fpga.cpp
new file mode 100644
index 00000000..3607f26e
--- /dev/null
+++ b/driver/opae/vlsim/fpga.cpp
@@ -0,0 +1,82 @@
+#include <stdint.h>
+#include <iostream>
+#include <stdio.h>
+#include <stdlib.h>
+#include <cstdlib>
+#include <unistd.h>
+#include <assert.h>
+#include "fpga.h"
+#include "opae_sim.h"
+#include <VX_config.h>
+
+extern fpga_result fpgaOpen(fpga_token token, fpga_handle *handle, int flags) {
+  if (NULL == handle || flags != 0)
+    return FPGA_INVALID_PARAM;
+  auto sim = new opae_sim();    
+  *handle = reinterpret_cast<fpga_handle>(sim);
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaClose(fpga_handle handle) {
+  if (NULL == handle)
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  delete sim;
+  
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaPrepareBuffer(fpga_handle handle, uint64_t len, void **buf_addr, uint64_t *wsid, int flags) {
+  if (NULL == handle || len == 0 || buf_addr == NULL || wsid == NULL) 
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  sim->prepare_buffer(len, buf_addr, wsid, flags);
+  
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaReleaseBuffer(fpga_handle handle, uint64_t wsid) {
+  if (NULL == handle) 
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  sim->release_buffer(wsid);
+
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaGetIOAddress(fpga_handle handle, uint64_t wsid, uint64_t *ioaddr) {
+  if (NULL == handle || ioaddr == NULL) 
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  sim->get_io_address(wsid, ioaddr);
+
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaWriteMMIO64(fpga_handle handle, uint32_t mmio_num, uint64_t offset, uint64_t value) {
+  if (NULL == handle || mmio_num != 0) 
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  sim->write_mmio64(mmio_num, offset, value);
+
+  return FPGA_OK;
+}
+
+extern fpga_result fpgaReadMMIO64(fpga_handle handle, uint32_t mmio_num, uint64_t offset, uint64_t *value) {
+  if (NULL == handle || mmio_num != 0 || value == NULL) 
+    return FPGA_INVALID_PARAM;
+
+  auto sim = reinterpret_cast<opae_sim*>(handle);
+  sim->read_mmio64(mmio_num, offset, value);
+
+  return FPGA_OK;
+}
+
+extern const char *fpgaErrStr(fpga_result e) {
+  return "";
+}
\ No newline at end of file
diff --git a/driver/opae/vlsim/fpga.h b/driver/opae/vlsim/fpga.h
new file mode 100644
index 00000000..e67c22b7
--- /dev/null
+++ b/driver/opae/vlsim/fpga.h
@@ -0,0 +1,48 @@
+#ifndef __FPGA_H__
+#define __FPGA_H__
+
+#include <stdio.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+	FPGA_OK = 0,         /**< Operation completed successfully */
+	FPGA_INVALID_PARAM,  /**< Invalid parameter supplied */
+	FPGA_BUSY,           /**< Resource is busy */
+	FPGA_EXCEPTION,      /**< An exception occurred */
+	FPGA_NOT_FOUND,      /**< A required resource was not found */
+	FPGA_NO_MEMORY,      /**< Not enough memory to complete operation */
+	FPGA_NOT_SUPPORTED,  /**< Requested operation is not supported */
+	FPGA_NO_DRIVER,      /**< Driver is not loaded */
+	FPGA_NO_DAEMON,      /**< FPGA Daemon (fpgad) is not running */
+	FPGA_NO_ACCESS,      /**< Insufficient privileges or permissions */
+	FPGA_RECONF_ERROR    /**< Error while reconfiguring FPGA */
+} fpga_result;
+
+typedef void *fpga_handle;
+
+typedef void *fpga_token;
+
+fpga_result fpgaOpen(fpga_token token, fpga_handle *handle, int flags);
+
+fpga_result fpgaClose(fpga_handle handle);
+
+fpga_result fpgaPrepareBuffer(fpga_handle handle, uint64_t len, void **buf_addr, uint64_t *wsid, int flags);
+
+fpga_result fpgaReleaseBuffer(fpga_handle handle, uint64_t wsid);
+
+fpga_result fpgaGetIOAddress(fpga_handle handle, uint64_t wsid, uint64_t *ioaddr);
+
+fpga_result fpgaWriteMMIO64(fpga_handle handle, uint32_t mmio_num, uint64_t offset, uint64_t value);
+
+fpga_result fpgaReadMMIO64(fpga_handle handle, uint32_t mmio_num, uint64_t offset, uint64_t *value);
+
+const char *fpgaErrStr(fpga_result e);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
+
+#endif // __FPGA_H__
diff --git a/driver/opae/vlsim/opae_sim.cpp b/driver/opae/vlsim/opae_sim.cpp
new file mode 100644
index 00000000..58debc6a
--- /dev/null
+++ b/driver/opae/vlsim/opae_sim.cpp
@@ -0,0 +1,261 @@
+#include "opae_sim.h"
+#include <iostream>
+#include <fstream>
+#include <iomanip>
+
+#define CCI_LATENCY 8
+#define CCI_RQ_SIZE 16
+#define CCI_WQ_SIZE 16
+
+#define ENABLE_DRAM_STALLS
+#define DRAM_LATENCY 4
+#define DRAM_RQ_SIZE 16
+#define DRAM_STALLS_MODULO 16
+
+uint64_t timestamp = 0;
+
+double sc_time_stamp() { 
+  return timestamp;
+}
+
+opae_sim::opae_sim() {  
+  // force random values for unitialized signals  
+  Verilated::randReset(2);
+  Verilated::randSeed(50);
+
+  // Turn off assertion before reset
+  Verilated::assertOn(false);
+
+  stop_ = false;
+  vortex_afu_ = new Vvortex_afu_shim();
+
+#ifdef VCD_OUTPUT
+  Verilated::traceEverOn(true);
+  trace_ = new VerilatedVcdC();
+  vortex_afu_->trace(trace_, 99);
+  trace_->open("trace.vcd");
+#endif  
+
+  future_ = std::async(std::launch::async, [&]{             
+      this->reset();
+      while (stop_) {
+          this->step();
+      }
+  });
+}
+
+opae_sim::~opae_sim() {  
+  stop_ = true;
+  if (future_.valid()) {
+    future_.wait();
+  }
+#ifdef VCD_OUTPUT
+  trace_->close();
+#endif     
+  delete vortex_afu_;
+}
+
+void opae_sim::prepare_buffer(uint64_t len, void **buf_addr, uint64_t *wsid, int flags) {
+  host_alloc_t alloc;
+  alloc.data = new uint8_t[len];
+  alloc.size = len;
+  *wsid = host_allocs_.size();
+  host_allocs_.push_back(alloc);
+}
+
+void opae_sim::release_buffer(uint64_t wsid) {
+  delete [] host_allocs_[wsid].data;
+  host_allocs_.erase(host_allocs_.begin() + wsid);
+}
+
+void opae_sim::get_io_address(uint64_t wsid, uint64_t *ioaddr) {
+  *ioaddr = (intptr_t)host_allocs_[wsid].data / GLOBAL_BLOCK_SIZE;
+}
+
+void opae_sim::write_mmio64(uint32_t mmio_num, uint64_t offset, uint64_t value) {
+  vortex_afu_->vcp2af_sRxPort_c0_mmioWrValid = 1;  
+  vortex_afu_->vcp2af_sRxPort_c0_hdr_resp_type = offset;
+  memcpy(vortex_afu_->vcp2af_sRxPort_c0_data, &value, 8);
+}
+
+void opae_sim::read_mmio64(uint32_t mmio_num, uint64_t offset, uint64_t *value) {
+  vortex_afu_->vcp2af_sRxPort_c0_mmioRdValid = 1;
+  vortex_afu_->vcp2af_sRxPort_c0_hdr_resp_type = offset;  
+  while (0 == vortex_afu_->af2cp_sTxPort_c2_mmioRdValid);
+  *value = vortex_afu_->af2cp_sTxPort_c2_data;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+void opae_sim::reset() {
+  vortex_afu_->clk = 0;
+  this->eval();
+
+  vortex_afu_->clk = 1;
+  this->eval();
+}
+
+void opae_sim::step() {
+  vortex_afu_->clk = 0;
+  this->eval();
+
+  vortex_afu_->clk = 1;
+  this->eval();
+
+  this->sRxPort_bus();
+  this->sTxPort_bus();
+  this->avs_bus();
+}
+
+void opae_sim::eval() {  
+  vortex_afu_->eval();
+#ifdef VCD_OUTPUT
+  trace_->dump(timestamp);
+#endif
+  ++timestamp;
+}
+
+void opae_sim::sRxPort_bus() {
+  // schedule CCI read responses
+  int cci_rd_index = -1;
+  for (int i = 0; i < cci_reads_.size(); i++) {
+    if (cci_reads_[i].cycles_left > 0) {
+      cci_reads_[i].cycles_left -= 1;
+    }
+    if ((cci_rd_index == -1) 
+     && (cci_reads_[i].cycles_left == 0)) {
+      cci_rd_index = i;
+    }
+  }
+
+  // schedule CCI write responses
+  int cci_wr_index = -1;
+  for (int i = 0; i < cci_writes_.size(); i++) {
+    if (cci_writes_[i].cycles_left > 0) {
+      cci_writes_[i].cycles_left -= 1;
+    }
+    if ((cci_wr_index == -1) 
+     && (cci_writes_[i].cycles_left == 0)) {
+      cci_wr_index = i;
+    }
+  }
+
+  // send CCI read response  
+  vortex_afu_->vcp2af_sRxPort_c0_rspValid = 0;  
+  if (cci_rd_index != -1) {
+    vortex_afu_->vcp2af_sRxPort_c0_rspValid = 1;
+    memcpy(vortex_afu_->vcp2af_sRxPort_c0_data, cci_reads_[cci_rd_index].block.data(), GLOBAL_BLOCK_SIZE);
+    vortex_afu_->vcp2af_sRxPort_c0_hdr_mdata = cci_reads_[cci_rd_index].mdata;
+    cci_reads_.erase(cci_reads_.begin() + cci_rd_index);
+  }
+
+  // send CCI write response  
+  vortex_afu_->vcp2af_sRxPort_c1_rspValid = 0;  
+  if (cci_wr_index != -1) {
+    vortex_afu_->vcp2af_sRxPort_c1_rspValid = 1;
+    vortex_afu_->vcp2af_sRxPort_c1_hdr_mdata = cci_writes_[cci_wr_index].mdata;
+    cci_writes_.erase(cci_writes_.begin() + cci_wr_index);
+  }
+
+  // mmio
+  vortex_afu_->vcp2af_sRxPort_c0_mmioWrValid = 0;
+  vortex_afu_->vcp2af_sRxPort_c0_mmioRdValid = 0;
+}
+  
+void opae_sim::sTxPort_bus() {
+  // check read queue size
+  vortex_afu_->vcp2af_sRxPort_c0_TxAlmFull = (cci_reads_.size() >= CCI_RQ_SIZE);
+
+  // check write queue size
+  vortex_afu_->vcp2af_sRxPort_c1_TxAlmFull = (cci_writes_.size() >= CCI_WQ_SIZE);
+
+  // process read requests
+  if (vortex_afu_->af2cp_sTxPort_c0_valid && !vortex_afu_->vcp2af_sRxPort_c0_TxAlmFull) {
+    cci_rd_req_t cci_req;
+    cci_req.cycles_left = CCI_LATENCY;     
+    cci_req.mdata = vortex_afu_->af2cp_sTxPort_c0_hdr_mdata;
+    auto host_ptr = this->find_host_ptr(vortex_afu_->af2cp_sTxPort_c0_hdr_address);
+    memcpy(cci_req.block.data(), host_ptr, GLOBAL_BLOCK_SIZE);
+    cci_reads_.push_back(cci_req);
+  }
+
+  // process write requests
+  if (vortex_afu_->af2cp_sTxPort_c1_valid && !vortex_afu_->vcp2af_sRxPort_c1_TxAlmFull) {
+    cci_wr_req_t cci_req;
+    cci_req.cycles_left = CCI_LATENCY;     
+    cci_req.mdata = vortex_afu_->af2cp_sTxPort_c1_hdr_mdata;
+    auto host_ptr = this->find_host_ptr(vortex_afu_->af2cp_sTxPort_c1_hdr_address);
+    memcpy(host_ptr, vortex_afu_->af2cp_sTxPort_c1_data, GLOBAL_BLOCK_SIZE);
+    cci_writes_.push_back(cci_req);
+  } 
+}
+  
+void opae_sim::avs_bus() {
+  // schedule DRAM read responses
+  int dram_rd_index = -1;
+  for (int i = 0; i < dram_reads_.size(); i++) {
+    if (dram_reads_[i].cycles_left > 0) {
+      dram_reads_[i].cycles_left -= 1;
+    }
+    if ((dram_rd_index == -1) 
+     && (dram_reads_[i].cycles_left == 0)) {
+      dram_rd_index = i;
+    }
+  }
+
+  // send DRAM response  
+  vortex_afu_->avs_readdatavalid = 0;  
+  if (dram_rd_index != -1) {
+    vortex_afu_->avs_readdatavalid = 1;
+    memcpy(vortex_afu_->avs_readdata, dram_reads_[dram_rd_index].block.data(), GLOBAL_BLOCK_SIZE);
+    dram_reads_.erase(dram_reads_.begin() + dram_rd_index);
+  }
+
+  // handle DRAM stalls
+  bool dram_stalled = false;
+#ifdef ENABLE_DRAM_STALLS
+  if (0 == ((timestamp/2) % DRAM_STALLS_MODULO)) { 
+    dram_stalled = true;
+  } else
+  if (dram_reads_.size() >= DRAM_RQ_SIZE) {
+    dram_stalled = true;
+  }
+#endif
+
+  // process DRAM requests
+  if (!dram_stalled) {
+    if (vortex_afu_->avs_write) {
+      assert(0 == vortex_afu_->mem_bank_select);
+      uint64_t byteen = vortex_afu_->avs_byteenable;
+      unsigned base_addr = (vortex_afu_->avs_address * GLOBAL_BLOCK_SIZE);
+      uint8_t* data = (uint8_t*)(vortex_afu_->avs_writedata);
+      for (int i = 0; i < GLOBAL_BLOCK_SIZE; i++) {
+        if ((byteen >> i) & 0x1) {            
+          ram_[base_addr + i] = data[i];
+        }
+      }
+    }
+    if (vortex_afu_->avs_read) {
+      assert(0 == vortex_afu_->mem_bank_select);
+      dram_rd_req_t dram_req;
+      dram_req.cycles_left = DRAM_LATENCY;     
+      ram_.read(vortex_afu_->avs_address * GLOBAL_BLOCK_SIZE, GLOBAL_BLOCK_SIZE, dram_req.block.data());
+      dram_reads_.push_back(dram_req);
+    }   
+  }
+
+  vortex_afu_->avs_waitrequest = dram_stalled;
+}
+
+uint8_t* opae_sim::find_host_ptr(uint64_t addr) {
+  auto b_addr = addr * GLOBAL_BLOCK_SIZE;
+  for (auto& host_alloc : host_allocs_) {
+    auto alloc_addr = (intptr_t)host_alloc.data;
+    if (b_addr >= alloc_addr 
+     && b_addr < (alloc_addr + host_alloc.size)) {
+      return (uint8_t*)b_addr;
+    }
+  }
+  assert(false);
+  return nullptr;
+}
\ No newline at end of file
diff --git a/driver/opae/vlsim/opae_sim.h b/driver/opae/vlsim/opae_sim.h
new file mode 100644
index 00000000..8467af42
--- /dev/null
+++ b/driver/opae/vlsim/opae_sim.h
@@ -0,0 +1,87 @@
+#pragma once
+
+#include "Vvortex_afu_shim.h"
+#include "Vvortex_afu_shim__Syms.h"
+#include "verilated.h"
+
+#ifdef VCD_OUTPUT
+#include <verilated_vcd_c.h>
+#endif
+
+#include <VX_config.h>
+#include "ram.h"
+
+#include <ostream>
+#include <future>
+#include <vector>
+
+class opae_sim {
+public:
+  
+  opae_sim();
+  virtual ~opae_sim();
+
+  void prepare_buffer(uint64_t len, void **buf_addr, uint64_t *wsid, int flags);
+
+  void release_buffer(uint64_t wsid);
+
+  void get_io_address(uint64_t wsid, uint64_t *ioaddr);
+
+  void write_mmio64(uint32_t mmio_num, uint64_t offset, uint64_t value);
+
+  void read_mmio64(uint32_t mmio_num, uint64_t offset, uint64_t *value);
+
+private: 
+
+  typedef struct {
+    int cycles_left;  
+    std::array<uint8_t, GLOBAL_BLOCK_SIZE> block;
+    unsigned tag;
+  } dram_rd_req_t;
+
+  typedef struct {
+    int cycles_left;  
+    std::array<uint8_t, GLOBAL_BLOCK_SIZE> block;
+    unsigned mdata;
+  } cci_rd_req_t;
+
+  typedef struct {
+    int cycles_left;  
+    std::array<uint8_t, GLOBAL_BLOCK_SIZE> block;
+    unsigned mdata;
+  } cci_wr_req_t;
+
+  typedef struct {    
+    uint8_t* data;
+    size_t size;  
+  } host_alloc_t;
+
+  void reset();
+
+  void eval();
+
+  void step();
+
+  void sRxPort_bus();
+  void sTxPort_bus();
+  void avs_bus();
+
+  uint8_t* find_host_ptr(uint64_t addr);
+
+  std::future<void> future_;
+  bool stop_;
+
+  std::vector<host_alloc_t> host_allocs_;
+
+  std::vector<dram_rd_req_t> dram_reads_;
+
+  std::vector<cci_rd_req_t> cci_reads_;
+
+  std::vector<cci_wr_req_t> cci_writes_;
+
+  RAM ram_;
+  Vvortex_afu_shim *vortex_afu_;
+#ifdef VCD_OUTPUT
+  VerilatedVcdC *trace_;
+#endif
+};
\ No newline at end of file
diff --git a/driver/opae/vlsim/ram.h b/driver/opae/vlsim/ram.h
new file mode 100644
index 00000000..53df7e0f
--- /dev/null
+++ b/driver/opae/vlsim/ram.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <stdio.h>
+#include <stdint.h>
+
+class RAM {
+private:
+
+  mutable uint8_t *mem_[(1 << 12)];      
+
+  uint8_t *get(uint32_t address) const {
+    uint32_t block_addr   = address >> 20;
+    uint32_t block_offset = address & 0x000FFFFF;
+    if (mem_[block_addr] == NULL) {
+      mem_[block_addr] = new uint8_t[(1 << 20)];
+    }
+    return mem_[block_addr] + block_offset;
+  }
+
+public:
+
+  RAM() {
+    for (uint32_t i = 0; i < (1 << 12); i++) {
+      mem_[i] = NULL;
+    }
+  }
+
+  ~RAM() {
+    this->clear();
+  }
+
+  size_t size() const {
+    return (1ull << 32);
+  }
+
+  void clear() {
+    for (uint32_t i = 0; i < (1 << 12); i++) {
+      if (mem_[i]) {
+        delete mem_[i];
+        mem_[i] = NULL;
+      }
+    }
+  }
+
+  void read(uint32_t address, uint32_t length, uint8_t *data) const {
+    for (unsigned i = 0; i < length; i++) {
+      data[i] = *this->get(address + i);
+    }
+  }
+
+  void write(uint32_t address, uint32_t length, const uint8_t *data) {
+    for (unsigned i = 0; i < length; i++) {
+      *this->get(address + i) = data[i];
+    }
+  }
+
+  uint8_t& operator[](uint32_t address) {
+    return *get(address);
+  }
+
+  const uint8_t& operator[](uint32_t address) const {
+    return *get(address);
+  }
+};
\ No newline at end of file
diff --git a/driver/opae/vlsim/verilator.vlt b/driver/opae/vlsim/verilator.vlt
new file mode 100644
index 00000000..cb799b65
--- /dev/null
+++ b/driver/opae/vlsim/verilator.vlt
@@ -0,0 +1,9 @@
+`verilator_config
+
+lint_off -rule BLKANDNBLK -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule UNOPTFLAT -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule WIDTH -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule UNUSED -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule LITENDIAN -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule IMPORTSTAR -file "../../../hw/rtl/fp_cores/fpnew/*"
+lint_off -rule PINCONNECTEMPTY -file "../../../hw/rtl/fp_cores/fpnew/*"
\ No newline at end of file
diff --git a/hw/opae/vortex_afu_sim.v b/driver/opae/vlsim/vortex_afu_shim.sv
similarity index 99%
rename from hw/opae/vortex_afu_sim.v
rename to driver/opae/vlsim/vortex_afu_shim.sv
index d3f9d8e1..ce007856 100644
--- a/hw/opae/vortex_afu_sim.v
+++ b/driver/opae/vlsim/vortex_afu_shim.sv
@@ -1,11 +1,11 @@
 `include "vortex_afu.vh"
-
+`include "VX_define.vh"
 /* verilator lint_off IMPORTSTAR */ 
 import ccip_if_pkg::*;
 import local_mem_cfg_pkg::*;
 /* verilator lint_on IMPORTSTAR */ 
 
-module vortex_afu_sim #(
+module vortex_afu_shim #(
   parameter NUM_LOCAL_MEM_BANKS = 2
 ) (
   // global signals
diff --git a/driver/opae/vortex.cpp b/driver/opae/vortex.cpp
index e66b9afe..a5174316 100755
--- a/driver/opae/vortex.cpp
+++ b/driver/opae/vortex.cpp
@@ -6,13 +6,20 @@
 #include <unistd.h>
 #include <assert.h>
 #include <cmath>
-#include <uuid/uuid.h>
+
+#ifdef USE_VLSIM
+#include "vlsim/fpga.h"
+#else
 #include <opae/fpga.h>
+#include <uuid/uuid.h>
+#endif
+
 #include <vortex.h>
 #include <VX_config.h>
 #include "vortex_afu.h"
+
 #ifdef SCOPE
-#include "scope.h"
+#include "vx_scope.h"
 #endif
 
 #define CACHE_LINESIZE  64
@@ -122,14 +129,16 @@ extern int vx_dev_caps(vx_device_h hdevice, unsigned caps_id, unsigned *value) {
 extern int vx_dev_open(vx_device_h* hdevice) {
     if (nullptr == hdevice)
         return  -1;
-        
-    fpga_properties filter = nullptr;
-    fpga_result res;
-    fpga_guid guid;
-    fpga_token accel_token;
-    uint32_t num_matches;
-    fpga_handle accel_handle;
+
+    fpga_result res;    
+    fpga_handle accel_handle;    
     vx_device_t* device;   
+
+#ifndef USE_VLSIM
+    fpga_token accel_token;
+    fpga_properties filter = nullptr;    
+    fpga_guid guid; 
+    uint32_t num_matches;
     
     // Set up a filter that will search for an accelerator
     fpgaGetProperties(nullptr, &filter);
@@ -159,6 +168,13 @@ extern int vx_dev_open(vx_device_h* hdevice) {
 
     // Done with token
     fpgaDestroyToken(&accel_token);
+#else
+    // Open accelerator
+    res = fpgaOpen(NULL, &accel_handle, 0);
+    if (FPGA_OK != res) {
+        return -1;
+    }
+#endif
 
     // allocate device object
     device = (vx_device_t*)malloc(sizeof(vx_device_t));
diff --git a/driver/opae/vortex_afu.h b/driver/opae/vortex_afu.h
new file mode 100644
index 00000000..c31e1a9e
--- /dev/null
+++ b/driver/opae/vortex_afu.h
@@ -0,0 +1,30 @@
+//
+// Generated by afu_json_mgr from ../../hw/opae/vortex_afu.json
+//
+
+#ifndef __AFU_JSON_INFO__
+#define __AFU_JSON_INFO__
+
+#define AFU_ACCEL_NAME "vortex_afu"
+#define AFU_ACCEL_UUID "35F9452B-25C2-434C-93D5-6F8C60DB361C"
+#define AFU_IMAGE_CMD_CLFLUSH 4
+#define AFU_IMAGE_CMD_CSR_READ 5
+#define AFU_IMAGE_CMD_CSR_WRITE 6
+#define AFU_IMAGE_CMD_MEM_READ 1
+#define AFU_IMAGE_CMD_MEM_WRITE 2
+#define AFU_IMAGE_CMD_RUN 3
+#define AFU_IMAGE_MMIO_CMD_TYPE 10
+#define AFU_IMAGE_MMIO_CSR_ADDR 26
+#define AFU_IMAGE_MMIO_CSR_CORE 24
+#define AFU_IMAGE_MMIO_CSR_DATA 28
+#define AFU_IMAGE_MMIO_CSR_READ 30
+#define AFU_IMAGE_MMIO_DATA_SIZE 16
+#define AFU_IMAGE_MMIO_IO_ADDR 12
+#define AFU_IMAGE_MMIO_MEM_ADDR 14
+#define AFU_IMAGE_MMIO_SCOPE_READ 20
+#define AFU_IMAGE_MMIO_SCOPE_WRITE 22
+#define AFU_IMAGE_MMIO_STATUS 18
+#define AFU_IMAGE_POWER 0
+#define AFU_TOP_IFC "ccip_std_afu_avalon_mm"
+
+#endif // __AFU_JSON_INFO__
diff --git a/driver/opae/scope.cpp b/driver/opae/vx_scope.cpp
similarity index 98%
rename from driver/opae/scope.cpp
rename to driver/opae/vx_scope.cpp
index 6b12a7ab..41709e37 100644
--- a/driver/opae/scope.cpp
+++ b/driver/opae/vx_scope.cpp
@@ -4,8 +4,15 @@
 #include <chrono>
 #include <vector>
 #include <assert.h>
+
+#ifdef USE_VLSIM
+#include "vlsim/fpga.h"
+#else
+#include <opae/fpga.h>
+#endif
+
 #include <VX_config.h>
-#include "scope.h"
+#include "vx_scope.h"
 #include "vortex_afu.h"
 
 #define CHECK_RES(_expr)                            \
@@ -18,12 +25,6 @@
      return -1;                                     \
    } while (false)
 
-
-template<int N> 
-constexpr bool static_print() {
-    return (0 < N < 100); 
-}
-
 #define MMIO_SCOPE_READ     (AFU_IMAGE_MMIO_SCOPE_READ * 4)
 #define MMIO_SCOPE_WRITE    (AFU_IMAGE_MMIO_SCOPE_WRITE * 4)
 
@@ -33,8 +34,7 @@ struct scope_signal_t {
 };
 
 constexpr int ilog2(int n) {
-    return (n > 1) ? 1 +
-     ilog2(n >> 1) : 0;
+    return (n > 1) ? 1 + ilog2(n >> 1) : 0;
 }
 
 static constexpr int NW_BITS = ilog2(NUM_WARPS);
diff --git a/driver/opae/scope.h b/driver/opae/vx_scope.h
similarity index 84%
rename from driver/opae/scope.h
rename to driver/opae/vx_scope.h
index 0d9dd2d2..f2d5518e 100644
--- a/driver/opae/scope.h
+++ b/driver/opae/vx_scope.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include <opae/fpga.h>
-
 int vx_scope_start(fpga_handle hfpga, uint64_t delay = -1);
 
 int vx_scope_stop(fpga_handle hfpga, uint64_t delay = -1);
\ No newline at end of file
diff --git a/driver/rtlsim/Makefile b/driver/rtlsim/Makefile
index d3d0df94..ec4252b5 100644
--- a/driver/rtlsim/Makefile
+++ b/driver/rtlsim/Makefile
@@ -22,7 +22,6 @@ DBG_FLAGS += -DDBG_CORE_REQ_INFO
 CONFIGS += -DNUM_CLUSTERS=1 -DNUM_CORES=1
 
 #DEBUG=1
-#AFU=1
 
 CFLAGS += -fPIC
 
@@ -35,11 +34,13 @@ LDFLAGS += -shared -pthread
 
 TOP = Vortex
 
-SRCS = vortex.cpp ../common/vx_utils.cpp ../../hw/simulate/simulator.cpp
-SRCS += ../../hw/rtl/fp_cores/svdpi/float_dpi.cpp
+RTL_DIR = ../../hw/rtl
 
-FPU_INCLUDE = -I../../hw/rtl/fp_cores -I../../hw/rtl/fp_cores/svdpi -I../../hw/rtl/fp_cores/fpnew/src/common_cells/include -I../../hw/rtl/fp_cores/fpnew/src/common_cells/src -I../../hw/rtl/fp_cores/fpnew/src/fpu_div_sqrt_mvp/hdl -I../../hw/rtl/fp_cores/fpnew/src 
-RTL_INCLUDE = -I../../hw/rtl -I../../hw/rtl/libs -I../../hw/rtl/interfaces -I../../hw/rtl/cache $(FPU_INCLUDE)
+SRCS = vortex.cpp ../common/vx_utils.cpp ../../hw/simulate/simulator.cpp
+SRCS += $(RTL_DIR)/fp_cores/svdpi/float_dpi.cpp
+
+FPU_INCLUDE = -I$(RTL_DIR)/fp_cores -I$(RTL_DIR)/fp_cores/svdpi -I$(RTL_DIR)/fp_cores/fpnew/src/common_cells/include -I$(RTL_DIR)/fp_cores/fpnew/src/common_cells/src -I$(RTL_DIR)/fp_cores/fpnew/src/fpu_div_sqrt_mvp/hdl -I$(RTL_DIR)/fp_cores/fpnew/src 
+RTL_INCLUDE = -I$(RTL_DIR) -I$(RTL_DIR)/libs -I$(RTL_DIR)/interfaces -I$(RTL_DIR)/cache $(FPU_INCLUDE)
 
 VL_FLAGS += --language 1800-2009 --assert -Wall -Wpedantic $(CONFIGS)
 VL_FLAGS += -Wno-DECLFILENAME
@@ -59,16 +60,6 @@ else
 	CFLAGS   += -DNDEBUG
 endif
 
-# AFU
-ifdef AFU
-    TOP = vortex_afu_sim
-	VL_FLAGS += -DNOPAE
-	CFLAGS += -DNOPAE
-	VL_FLAGS += -DSCOPE
-	CFLAGS += -DSCOPE
-	RTL_INCLUDE += -I../../hw/opae  -I../../hw/opae/ccip
-endif
-
 PROJECT = libvortex.so
 # PROJECT = libvortex.dylib
 
diff --git a/hw/simulate/simulator.cpp b/hw/simulate/simulator.cpp
index 99a5599f..a6d90dbd 100644
--- a/hw/simulate/simulator.cpp
+++ b/hw/simulate/simulator.cpp
@@ -3,6 +3,11 @@
 #include <fstream>
 #include <iomanip>
 
+#define ENABLE_DRAM_STALLS
+#define DRAM_LATENCY 4
+#define DRAM_RQ_SIZE 16
+#define DRAM_STALLS_MODULO 16
+
 uint64_t timestamp = 0;
 
 double sc_time_stamp() { 
diff --git a/hw/simulate/simulator.h b/hw/simulate/simulator.h
index a16218bb..f43e1d8b 100644
--- a/hw/simulate/simulator.h
+++ b/hw/simulate/simulator.h
@@ -14,17 +14,6 @@
 #include <ostream>
 #include <vector>
 
-#define ENABLE_DRAM_STALLS
-#define DRAM_LATENCY 4
-#define DRAM_RQ_SIZE 16
-#define DRAM_STALLS_MODULO 16
-
-typedef struct {
-  int cycles_left;  
-  std::array<uint8_t, GLOBAL_BLOCK_SIZE> block;
-  unsigned tag;
-} dram_req_t;
-
 class Simulator {
 public:
   
@@ -53,6 +42,12 @@ public:
 
 private:  
 
+  typedef struct {
+    int cycles_left;  
+    std::array<uint8_t, GLOBAL_BLOCK_SIZE> block;
+    unsigned tag;
+  } dram_req_t;
+
   void eval();  
 
   void eval_dram_bus();
@@ -61,7 +56,7 @@ private:
   void eval_snp_bus();
   
   std::vector<dram_req_t> dram_rsp_vec_;
-  int dram_rsp_active_;
+  bool dram_rsp_active_;
   
   bool snp_req_active_;
   bool csr_req_active_;