Personal computer using flash memory as BIOS-ROM

Claim 1

A personal computer comprising: a BIOS-ROM comprising a flash memory having a first storage area which reserves a read-only boot area and a second storage area which stores a first basic input/output system, said first and second storage areas being distinguished from each other by a predetermined bit of address data, a far jump instruction being stored in a predetermined location of said boot area; an external storage device for storing a second basic input/output system; data processing means for, immediately after power-on reset, outputting predetermined address data to access said boot area of said BIOS-ROM, thereby executing said far jump instruction and for, after system startup, outputting address data differing from said predetermined address data, wherein the address data output after system startup includes address data used to access said first storage area of said BIOS-ROM, thereby performing operations according to said first basic input/output system stored in said BIOS-ROM; address translating means, connected to said data processing means to receive the address data output from said data processing means after system startup, wherein said address data includes said predetermined bit of address data which distinguishes said first storage area and said second storage area, and for inverting a logical value of said predetermined bit and outputting the address data including the inverted bit to said BIOS-ROM; masking means connected to said data processing means for masking address data output from said data processing means which designates said second storage area, thereby preventing said BIOS-ROM from being accessed after system startup; instruction inputting means for inputting a transfer instruction to transfer said second basic input/output system from said external storage device to said BIOS-ROM; first determining means for determining, by virtue of the execution of said far jump instruction, whether or not said transfer instruction is input from said inputting means; second determining means for determining whether stored data of said BIOS-ROM is correct or not when said first determining means determines that said transfer instruction is not input from said inputting means; means for setting said address translating means and said masking means to an enabled state when said second determining means determines that the stored data of said BIOS-ROM is correct; and means for transferring said second basic input/output system from said external storage device to said BIOS-ROM to rewrite said first basic input/output system stored in said BIOS-ROM in a first case when said first determining means determines that said transfer instruction has been input from said inputting means and in a second case when said first determining means determines that no transfer instruction is input from said inputting means and said second determining means determines that the stored data of said BIOS-ROM is incorrect, wherein said second basic input/output system is automatically transferred from said external storage device to said BIOS-ROM in said second case.