diff --git a/abstract-machine/am/src/riscv/npc/npc.h b/abstract-machine/am/src/riscv/npc/npc.h
new file mode 100644
index 0000000..e6c0241
--- /dev/null
+++ b/abstract-machine/am/src/riscv/npc/npc.h
@@ -0,0 +1,6 @@
+#ifndef _AM_NPC_NPC_H_
+#define _AM_NPC_NPC_H_
+#define SERIAL_PORT 0x10000000
+#define RTC_ADDR 0x10001000
+
+#endif
\ No newline at end of file
diff --git a/flake.nix b/flake.nix
index 58652b3..0ea12c7 100644
--- a/flake.nix
+++ b/flake.nix
@@ -86,7 +86,8 @@
           inputsFrom = [
             self.packages.${system}.nemu
           ];
-          IMAGES_PATH = "${self.packages.${system}.am-kernels}/share/binary";
+          NEMU_HOME = "/home/xin/repo/ysyx-workbench/nemu";
+          NEMU_IMAGES_PATH = self.packages.${system}.am-kernels + "/share/am-kernels";
         };
 
         devShells.npc = with pkgs; mkShell.override { stdenv = ccacheStdenv; } {
diff --git a/nemu/default.nix b/nemu/default.nix
index e6ffb2b..785d77e 100644
--- a/nemu/default.nix
+++ b/nemu/default.nix
@@ -43,7 +43,7 @@ stdenv.mkDerivation rec {
 
   doCheck = (defconfig == "alldefconfig");
   checkPhase = if doCheck then ''
-    export IMAGES_PATH=${am-kernels}/share/binary
+    export NEMU_IMAGES_PATH=${am-kernels}/share/am-kernels
     make test
   '' else "";
 
diff --git a/nemu/src/isa/riscv64 b/nemu/src/isa/riscv64
deleted file mode 120000
index 4eb3f6d..0000000
--- a/nemu/src/isa/riscv64
+++ /dev/null
@@ -1 +0,0 @@
-riscv32
\ No newline at end of file
diff --git a/nemu/src/monitor/filelist.mk b/nemu/src/monitor/filelist.mk
index 4094bee..07c4fe5 100644
--- a/nemu/src/monitor/filelist.mk
+++ b/nemu/src/monitor/filelist.mk
@@ -1,3 +1,3 @@
-DIRS-y += src/monitor/monitor.c
+DIRS-y += src/monitor
 
 CXXSRC += src/monitor/gdbstub.cc
diff --git a/nemu/src/monitor/monitor.c b/nemu/src/monitor/monitor.c
index 9f49786..b9b343e 100644
--- a/nemu/src/monitor/monitor.c
+++ b/nemu/src/monitor/monitor.c
@@ -13,8 +13,10 @@
 * See the Mulan PSL v2 for more details.
 ***************************************************************************************/
 
+#include <errno.h>
 #include <isa.h>
 #include <memory/paddr.h>
+#include <strings.h>
 #include <utils.h>
 
 void init_rand();
@@ -48,13 +50,50 @@ static char *img_file = NULL;
 static int difftest_port = 1234;
 
 static long load_img() {
+  FILE *fp = NULL;
+  size_t img_filename_len = strlen(img_file);
   if (img_file == NULL) {
     Log("No image is given. Use the default build-in image.");
     return 4096; // built-in image size
   }
 
-  FILE *fp = fopen(img_file, "rb");
-  Assert(fp, "Can not open '%s'", img_file);
+  // Image file is searched from paths in environment variable NEMU_IMAGES_PATH if it's a relative path
+  if (img_file[0] != '/') {
+    char *search_paths = getenv("NEMU_IMAGES_PATH");
+    if(search_paths == NULL) search_paths = "./";
+    search_paths = strdup(search_paths);
+    Trace("NEMU_IMAGES_PATH=%s", search_paths);
+
+    char *paths_end = strchr(search_paths, '\0');
+    char *p_start = search_paths;
+    do {
+      char *p = strchr(p_start, ':');
+      if (p != NULL) *p = '\0';
+      else p = paths_end;
+
+      char *file_path = malloc(p - p_start + img_filename_len + 2);
+      strcpy(file_path, p_start);
+      strcat(file_path, "/");
+      strcat(file_path, img_file);
+
+      fp = fopen(file_path, "rb");
+      free(file_path);
+
+      if (fp) {
+        Log("Found '%s' in '%s'", img_file, p_start);
+        break;
+      }
+
+      Assert(fp != NULL || errno == ENOENT, "Cannot open '%s'", img_file);
+      p_start = p + 1;
+    } while(p_start < paths_end);
+    free(search_paths);
+
+    Assert(fp, "Cannot find '%s'", img_file);
+  } else {
+    fp = fopen(img_file, "rb");
+    Assert(fp, "Cannot open '%s'", img_file);
+  }
 
   fseek(fp, 0, SEEK_END);
   long size = ftell(fp);
diff --git a/nemu/src/utils/filelist.mk b/nemu/src/utils/filelist.mk
index bcd69c5..2537b81 100644
--- a/nemu/src/utils/filelist.mk
+++ b/nemu/src/utils/filelist.mk
@@ -14,7 +14,7 @@
 #**************************************************************************************/
 
 ifneq ($(CONFIG_ITRACE)$(CONFIG_IQUEUE),)
-CXXSRC = src/utils/disasm.cc
+CXXSRC += src/utils/disasm.cc
 CXXFLAGS += $(shell llvm-config --cxxflags) -fPIE
 LIBS += $(shell llvm-config --libs)
 endif