diff --git a/bootloader/rustsbi-k210.bin b/bootloader/rustsbi-k210.bin
deleted file mode 100755
index c53ed1f..0000000
Binary files a/bootloader/rustsbi-k210.bin and /dev/null differ
diff --git a/os/Makefile b/os/Makefile
index ff2889b..b0c1fc7 100644
--- a/os/Makefile
+++ b/os/Makefile
@@ -5,14 +5,12 @@ KERNEL_ELF := target/$(TARGET)/$(MODE)/os
 KERNEL_BIN := $(KERNEL_ELF).bin
 DISASM_TMP := target/$(TARGET)/$(MODE)/asm
 FS_IMG := ../user/target/$(TARGET)/$(MODE)/fs.img
-SDCARD := /dev/sdb
 APPS := ../user/src/bin/*
 
 # BOARD
-BOARD ?= qemu
+BOARD := qemu
 SBI ?= rustsbi
 BOOTLOADER := ../bootloader/$(SBI)-$(BOARD).bin
-K210_BOOTLOADER_SIZE := 131072
 
 # Building mode argument
 ifeq ($(MODE), release)
@@ -20,15 +18,7 @@ ifeq ($(MODE), release)
 endif
 
 # KERNEL ENTRY
-ifeq ($(BOARD), qemu)
-	KERNEL_ENTRY_PA := 0x80200000
-else ifeq ($(BOARD), k210)
-	KERNEL_ENTRY_PA := 0x80020000
-endif
-
-# Run K210
-K210-SERIALPORT	= /dev/ttyUSB0
-K210-BURNER	= ../tools/kflash.py
+KERNEL_ENTRY_PA := 0x80200000
 
 # Binutils
 OBJDUMP := rust-objdump --arch-name=riscv64
@@ -40,14 +30,7 @@ DISASM ?= -x
 # Run usertests or usershell
 TEST ?=
 
-build: env switch-check $(KERNEL_BIN) fs-img 
-
-switch-check:
-ifeq ($(BOARD), qemu)
-	(which last-qemu) || (rm -f last-k210 && touch last-qemu && make clean)
-else ifeq ($(BOARD), k210)
-	(which last-k210) || (rm -f last-qemu && touch last-k210 && make clean)
-endif
+build: env $(KERNEL_BIN) fs-img 
 
 env:
 	(rustup target list | grep "riscv64gc-unknown-none-elf (installed)") || rustup target add $(TARGET)
@@ -55,11 +38,6 @@ env:
 	rustup component add rust-src
 	rustup component add llvm-tools-preview
 
-sdcard: fs-img
-	@echo "Are you sure write to $(SDCARD) ? [y/N] " && read ans && [ $${ans:-N} = y ]
-	@sudo dd if=/dev/zero of=$(SDCARD) bs=1048576 count=32
-	@sudo dd if=$(FS_IMG) of=$(SDCARD)
-
 $(KERNEL_BIN): kernel
 	@$(OBJCOPY) $(KERNEL_ELF) --strip-all -O binary $@
 
@@ -73,7 +51,7 @@ $(APPS):
 kernel:
 	@echo Platform: $(BOARD)
 	@cp src/linker-$(BOARD).ld src/linker.ld
-	@cargo build --release --features "board_$(BOARD)"
+	@cargo build --release
 	@rm src/linker.ld
 
 clean:
@@ -90,7 +68,6 @@ disasm-vim: kernel
 run: run-inner
 
 run-inner: build
-ifeq ($(BOARD),qemu)
 	@qemu-system-riscv64 \
 		-machine virt \
 		-nographic \
@@ -98,15 +75,6 @@ ifeq ($(BOARD),qemu)
 		-device loader,file=$(KERNEL_BIN),addr=$(KERNEL_ENTRY_PA) \
 		-drive file=$(FS_IMG),if=none,format=raw,id=x0 \
         -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0
-else
-	(which $(K210-BURNER)) || (cd .. && git clone https://github.com/sipeed/kflash.py.git && mv kflash.py tools)
-	@cp $(BOOTLOADER) $(BOOTLOADER).copy
-	@dd if=$(KERNEL_BIN) of=$(BOOTLOADER).copy bs=$(K210_BOOTLOADER_SIZE) seek=1
-	@mv $(BOOTLOADER).copy $(KERNEL_BIN)
-	@sudo chmod 777 $(K210-SERIALPORT)
-	python3 $(K210-BURNER) -p $(K210-SERIALPORT) -b 1500000 $(KERNEL_BIN)
-	python3 -m serial.tools.miniterm --eol LF --dtr 0 --rts 0 --filter direct $(K210-SERIALPORT) 115200
-endif
 
 debug: build
 	@tmux new-session -d \
@@ -121,4 +89,4 @@ gdbserver: build
 gdbclient:
 	@riscv64-unknown-elf-gdb -ex 'file $(KERNEL_ELF)' -ex 'set arch riscv:rv64' -ex 'target remote localhost:1234'
 
-.PHONY: build env kernel clean disasm disasm-vim run-inner switch-check fs-img gdbserver gdbclient
+.PHONY: build env kernel clean disasm disasm-vim run-inner fs-img gdbserver gdbclient
diff --git a/os/src/main.rs b/os/src/main.rs
index 5f8811a..cc58958 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -31,10 +31,6 @@ extern crate alloc;
 #[macro_use]
 extern crate bitflags;
 
-#[cfg(feature = "board_k210")]
-#[path = "boards/k210.rs"]
-mod board;
-#[cfg(not(any(feature = "board_k210")))]
 #[path = "boards/qemu.rs"]
 mod board;
 
diff --git a/os/src/sbi.rs b/os/src/sbi.rs
index a903da6..f5a0005 100644
--- a/os/src/sbi.rs
+++ b/os/src/sbi.rs
@@ -12,6 +12,7 @@ const SBI_REMOTE_FENCE_I: usize = 5;
 const SBI_REMOTE_SFENCE_VMA: usize = 6;
 const SBI_REMOTE_SFENCE_VMA_ASID: usize = 7;
 const SBI_SHUTDOWN: usize = 8;
+
 /// general sbi call
 #[inline(always)]
 fn sbi_call(which: usize, arg0: usize, arg1: usize, arg2: usize) -> usize {
diff --git a/os/src/task/mod.rs b/os/src/task/mod.rs
index 8849677..569cf74 100644
--- a/os/src/task/mod.rs
+++ b/os/src/task/mod.rs
@@ -59,7 +59,6 @@ pub fn suspend_current_and_run_next() {
 /// pid of usertests app in make run TEST=1
 pub const IDLE_PID: usize = 0;
 
-#[cfg(feature = "board_qemu")]
 use crate::board::QEMUExit;
 
 /// Exit the current 'Running' task and run the next task in task list.
@@ -67,9 +66,7 @@ pub fn exit_current_and_run_next(exit_code: i32) {
     // take from Processor
     let task = take_current_task().unwrap();
 
-    #[cfg(feature = "board_qemu")]
     let pid = task.getpid();
-    #[cfg(feature = "board_qemu")]
     if pid == IDLE_PID {
         println!(
             "[kernel] Idle process exit with exit_code {} ...",