diff --git a/board/freescale/bsc9131rdb/README b/board/freescale/bsc9131rdb/README
index 065faa3..d7b2176 100644
--- a/board/freescale/bsc9131rdb/README
+++ b/board/freescale/bsc9131rdb/README
@@ -89,10 +89,14 @@
 Building U-boot
 --------------
 To build the u-boot for BSC9131RDB:
-1. NAND Flash
+1. NAND Flash with sysclk 66MHz(J16 on RDB closed, default)
 	make BSC9131RDB_NAND
-2. SPI Flash
+2. NAND Flash with sysclk 100MHz(J16 on RDB open)
+	make BSC9131RDB_NAND_SYSCLK100
+3. SPI Flash with sysclk 66MHz(J16 on RDB closed, default)
 	make BSC9131RDB_SPIFLASH
+4. SPI Flash with sysclk 100MHz(J16 on RDB open)
+	make BSC9131RDB_SPIFLASH_SYSCLK100
 
 Memory map
 -----------