Please refer to FIG. 1, a functional block diagram illustrating a conventional computer system. The computer system includes a central processing unit (CPU) 10, a north bridge chip 11, a south bridge chip 12, first storage device 13 and second storage device 14. To boot the computer system, it is necessary to load both basic input/output system (BIOS) codes and operating system (OS) codes into a core circuit of the computer system. The BIOS codes and the OS codes are usually stored in different types of storage devices. For example, the BIOS codes 130 are usually stored in a read-only memory (the first storage device 13) while the OS codes 140 are usually stored in a hard disk drive (the second storage device 14). Hence, the first transmission interface 131 for data transmission between the south bridge chip 12 and the first storage device 13 is quite different from the second transmission interface 141 for data transmission between the south bridge chip 12 and the second storage device 14. For example, the first transmission interface 131 may be implemented with an industry standard architecture (ISA) interface, a low pin count (LPC) interface or a serial peripheral interface (SPI) while the second transmission interface 141 may be implemented with an integrated drive electronics (IDE) interface or a serial advanced technology attachment (SATA) interface.
Since two kinds of storage devices and two kinds of transmission interfaces are required, the wasteful duplication of the devices with similar functions is arranged in the computer system. Such arrangement causes higher cost and wastes more power. It adversely affects the energy efficiency and competitiveness. Hence, a computer system with an integrated storage device is desired to enhance the overall performance.