diff --git a/nemu/.config.old b/nemu/.config.old
new file mode 100644
index 0000000..1a17e6e
--- /dev/null
+++ b/nemu/.config.old
@@ -0,0 +1,74 @@
+#
+# Automatically generated file; DO NOT EDIT.
+# NEMU Configuration Menu
+#
+# CONFIG_ISA_x86 is not set
+# CONFIG_ISA_mips32 is not set
+CONFIG_ISA_riscv=y
+# CONFIG_ISA_loongarch32r is not set
+CONFIG_ISA="riscv32"
+
+#
+# ISA-dependent Options for riscv
+#
+# CONFIG_RV64 is not set
+# CONFIG_RVE is not set
+# end of ISA-dependent Options for riscv
+
+CONFIG_ENGINE_INTERPRETER=y
+CONFIG_ENGINE="interpreter"
+CONFIG_MODE_SYSTEM=y
+CONFIG_TARGET_NATIVE_ELF=y
+# CONFIG_TARGET_SHARE is not set
+# CONFIG_TARGET_AM is not set
+
+#
+# Build Options
+#
+CONFIG_CC_GCC=y
+# CONFIG_CC_GPP is not set
+# CONFIG_CC_CLANG is not set
+CONFIG_CC="gcc"
+# CONFIG_CC_O0 is not set
+# CONFIG_CC_O1 is not set
+CONFIG_CC_O2=y
+# CONFIG_CC_O3 is not set
+CONFIG_CC_OPT="-O2"
+# CONFIG_CC_LTO is not set
+# CONFIG_CC_DEBUG is not set
+# CONFIG_CC_ASAN is not set
+# end of Build Options
+
+#
+# Testing and Debugging
+#
+CONFIG_TRACE=y
+CONFIG_TRACE_START=0
+CONFIG_TRACE_END=10000
+CONFIG_ITRACE=y
+CONFIG_ITRACE_COND="true"
+# CONFIG_DIFFTEST is not set
+CONFIG_DIFFTEST_REF_PATH="none"
+CONFIG_DIFFTEST_REF_NAME="none"
+# end of Testing and Debugging
+
+#
+# Memory Configuration
+#
+CONFIG_MBASE=0x80000000
+CONFIG_MSIZE=0x8000000
+CONFIG_PC_RESET_OFFSET=0
+# CONFIG_PMEM_MALLOC is not set
+CONFIG_PMEM_GARRAY=y
+CONFIG_MEM_RANDOM=y
+# end of Memory Configuration
+
+# CONFIG_DEVICE is not set
+
+#
+# Miscellaneous
+#
+CONFIG_TIMER_GETTIMEOFDAY=y
+# CONFIG_TIMER_CLOCK_GETTIME is not set
+CONFIG_RT_CHECK=y
+# end of Miscellaneous