diff --git a/kernel/src/arch/aarch64/board/raspi3/fb.rs b/kernel/src/arch/aarch64/board/raspi3/fb.rs
index 5f9ba64..869b7eb 100644
--- a/kernel/src/arch/aarch64/board/raspi3/fb.rs
+++ b/kernel/src/arch/aarch64/board/raspi3/fb.rs
@@ -176,15 +176,44 @@ impl Framebuffer {
         }
     }
 
-    /// Clean screen
-    pub fn clear(&mut self) {
-        let mut start = self.base_addr();
-        let end = start + self.fb_info.screen_size as usize;
+    /// Copy buffer `[src_off .. src_off + size]` to `[dst_off .. dst_off + size]`.
+    /// `dst_off`, `src_off` and `size` must be aligned with `usize`.
+    pub fn copy(&mut self, dst_off: usize, src_off: usize, size: usize) {
+        const USIZE: usize = core::mem::size_of::<usize>();
+        let mut dst = self.base_addr() + dst_off;
+        let mut src = self.base_addr() + src_off;
+        let src_end = src + size;
+        while src < src_end {
+            unsafe { *(dst as *mut usize) = *(src as *mut usize) }
+            dst += USIZE;
+            src += USIZE;
+        }
+    }
+
+    /// Fill buffer `[offset .. offset + size]` with `pixel`.
+    /// `offset` and `size` must be aligned with `usize`.
+    pub fn fill(&mut self, offset: usize, size: usize, pixel: u32) {
+        const USIZE: usize = core::mem::size_of::<usize>();
+        let mut value: usize = 0;
+        let repeat = USIZE * 8 / self.fb_info.depth as usize;
+        let mask = ((1u64 << self.fb_info.depth) - 1) as usize;
+        for i in 0..repeat {
+            value <<= self.fb_info.depth;
+            value += pixel as usize & mask;
+        }
+
+        let mut start = self.base_addr() + offset;
+        let end = start + size;
         while start < end {
-            unsafe { *(start as *mut usize) = 0 }
-            start += core::mem::size_of::<usize>();
+            unsafe { *(start as *mut usize) = value }
+            start += USIZE;
         }
     }
+
+    /// Fill the entire buffer with `0`.
+    pub fn clear(&mut self) {
+        self.fill(0, self.fb_info.screen_size as usize, 0);
+    }
 }
 
 lazy_static! {
diff --git a/kernel/src/arch/aarch64/driver/console.rs b/kernel/src/arch/aarch64/driver/console.rs
index 209b45e..4822e41 100644
--- a/kernel/src/arch/aarch64/driver/console.rs
+++ b/kernel/src/arch/aarch64/driver/console.rs
@@ -9,10 +9,10 @@ use lazy_static::lazy_static;
 use log::*;
 use spin::Mutex;
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 struct Color(u8);
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 #[repr(C)]
 pub struct ConsoleChar {
     ascii_char: u8,
@@ -68,16 +68,23 @@ impl<F: Font> ConsoleBuffer<F> {
         self.write(row, col, ConsoleChar::default());
     }
 
-    /// Insert one blank line at the bottom and remove the top line.
-    /// TODO: improve performance
-    fn new_line(&mut self) {
+    /// Insert one blank line at the bottom, and scroll up one line.
+    /// XXX: read framebuffer is toooo slow, do not use `fb.copy()`.
+    pub fn new_line(&mut self) {
         for i in 1..self.num_row {
             for j in 0..self.num_col {
-                self.write(i - 1, j, self.buf[i][j]);
+                if self.buf[i - 1][j] != self.buf[i][j] {
+                    self.write(i - 1, j, self.buf[i][j]);
+                }
             }
         }
         for j in 0..self.num_col {
-            self.write(self.num_row - 1, j, ConsoleChar::default());
+            self.buf[self.num_row - 1][j] = ConsoleChar::default();
+        }
+
+        if let Some(fb) = FRAME_BUFFER.lock().as_mut() {
+            let rowbytes = F::HEIGHT * fb.fb_info.pitch as usize;
+            fb.fill(rowbytes * (self.num_row - 1), rowbytes, 0);
         }
     }