Address offset feature for a hard disk drive

• US 6,415,383 B1
• Filed: 10/06/1999
• Issued: 07/02/2002
• Est. Priority Date: 10/06/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kohno, Masaki, Colegrove, Dan, Smolin, Klaus, Malina, Alfred, Kobayashi, Kazuyuki, Roosen, Martin
• Primary Examiner(s): NGUYEN, THAN VINH
• Application Number:
  US09/414,301
• Time in Patent Office: 1,000 Days
• Field of Search: 711/100, 711/101, 711/4, 711/170, 711/173, 711/202, 713/2
• US Class Current: 713/2
• CPC Class Codes: G06F 9/441 Multiboot arrangements, i.e. selecting an operating system to be loaded

Abstract

A method of changing the operating system in a computer system by using an address offset mode (AOM) feature for the address space of a hard disk drive connected to the computer system. Initialization of the computer loads the first operating system (OS) from a user area in the disk drive address space. An enable AOM command offsets the disk drive address space and reinitializes the computer to load a second OS from a reserve space in the disk drive address space. A command setting the maximum size of the address space of the hard disk drive provides a wrap around feature allowing the entire address space of the disk drive to be addressable for diagnostics or updating purposes. The computer is returned to operation with the first OS by a disable AOM command, or alternatively, by a power on reset, a software reset or a hardware reset. The method of changing operating systems is coded in the hard disk drive and does not require additions or modifications to the memory or the BIOS ROM of the computer system.

Claims

1. A method of changing operating systems of a computer system having a disk drive for providing data storage, comprising the steps of:

storing a first operating system in an address space of the disk drive in a user area having a first logical block address (LBA) at the absolute address zero of the disk drive;

establishing a nonvolatile reserved area in the disk drive having a second LBA, the second LBA following sequentially after the user area;

storing a second operating system in the disk drive in the reserved area; and

upon initializing the computer system;

(A) loading the first OS from the user area at the absolute address zero of the disk drive;

(B) enabling an address offset mode (AOM) offsetting the address space of the disk drive by the difference of the second LBA and the first LBA;

(C) loading the second OS from the reserved area by reinitializing the computer system;

(D) disabling the address offset mode (AOM) while operating the computer system under the second OS by removing the offset to the address space of the disk drive;

(E) setting a maximum allowed address for the address space to the maximum address in the address space to provide access to the entire address space of the disk drive; and

,

(F) reloading the first OS from the user area of the disk drive by reinitializing the computer system.

2. The method of changing the operating systems in a computer system as recited in claim 1, wherein the step of disabling the address offset mode is accomplished by using a disable address offset mode command.

3. The method of changing the operating systems in a computer system as recited in claim 1, wherein the step of disabling the address offset mode is accomplished by using a command chosen from a group consisting of a power on reset command, software reset command and a hardware reset command.

4. An article of manufacture comprising a machine readable memory having stored therein a plurality of machine executable control program steps for changing operating systems of a personal computer system having a disk drive for providing data storage, said plurality of stored machine executable control program steps include:

a control program step for storing a first operating system in an address space of the disk drive in a user area having a first logical block address (LBA) at the absolute address zero of the disk drive;

a control program step for establishing a nonvolatile reserved area in the disk drive having a second LBA, the second LBA following sequentially after the user area;

a control program step for storing a second operating system in the disk drive in the reserved area; and

upon initializing the computer system;

(A) a control program step for loading the first OS from the user area at the absolute address zero of the disk drive;

(B) a control program step for enabling an address offset mode (AOM) offsetting the address space of the disk drive by the difference of the second LBA and the first LBA;

(C) a control program step for loading the second OS from the reserved by reinitializing the computer system;

(D) a control program step for disabling the address offset mode (AOM) while operating the computer system under the second OS by removing the offset to the address space of the disk drive;

(D) a control program step for setting a maximum allowed address for the address space to the maximum address in the address space to provide access to the entire address space of the disk drive; and

,

(E) a control program step for reloading the first OS from the user area of the disk file by reinitializing the computer system.

5. An article of manufacture as recited in claim 4, wherein the control program step for disabling the address offset mode is accomplished by using a disable address offset mode command.

6. An article of manufacture as recited in claim 4, wherein the control program step for disabling the address offset mode is accomplished by using a command chosen from a group consisting of a power on reset command, software reset command and a hardware reset command.