Small computer system emulator for non-local SCSI devices

• US 5,721,880 A
• Filed: 02/20/1996
• Issued: 02/24/1998
• Est. Priority Date: 12/20/1991
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wachtel, Edward Irving, McNeill, Andrew Boyce Jr.
• Primary Examiner(s): Bowler, Alyssa H.
• Assistant Examiner(s): Nguyen, Dzung C.
• Application Number:
  US08/603,660
• Time in Patent Office: 735 Days
• Field of Search: 395/800, 395/500, 395/112, 395/551, 395/727, 364/DIG. 1
• US Class Current: 703/25
• CPC Class Codes: G06F 13/102 where the programme performs an interfacing function, e.g. device driver G06F13/105 takes precedence; scheduling within device drivers G06F9/52; contention policies within device drivers G06F9/4881
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

A SCSI computer system is provided whereby a host computer gains access to a targeted but non-local peripheral device, which device or devices are individually responsive to either SCSI or non-SCSI commands, by sending SCSI commands via a SCSI bus to a connected SCSI target computer which emulates the targeted peripheral device local to the SCSI target computer, whether the targeted peripheral device is responsive to only SCSI or only non-SCSI commands, to cause the targeted peripheral device to carry out the initial SCSI commands.

Claims

1. A computer network system for accessing a peripheral device where the peripheral device is not directly connected to a bus locally connected to an accessing computer and is connected to another target computer having a memory resident emulation program and which shares a common Small Computer System Interface bus with the accessing computer, comprising:

a Small Computer System Interface (SCSI) bus;

an initiator accessing computer connected to the SCSI bus for generating and sending SCSI commands along the SCSI bus for accessing a targeted peripheral device non-local to the initiator accessing computer; and

a target computer connected to the SCSI bus for receiving the SCSI commands and in response to the SCSI commands sent via the SCSI bus from the initiator accessing computer for the memory resident emulation program in the target computer to emulate a non SCSI peripheral device being accessed by the initiator accessing computer, to generate target commands to access a non-SCSI targeted peripheral device, and for the memory resident emulation program to emulate a SCSI peripheral device being accessed by the initiator accessing computer to generate the target commands to access a SCSI targeted peripheral device, and for providing synchronization of the commands between the initiator accessing computer and the target computer and for performance of the SCSI commands by the targeted peripheral device, and the targeted peripheral device non-local to the initiator accessing computer receiving the target commands from the target computer generated in response to and for performance of the generated SCSI commands.

2. A computer network system of two computers wherein the first computer accesses a remote peripheral device of the second computer, comprising:

a first computer including a first Small Computer System Interface (SCSI) adapter;

a second computer including a second SCSI adapter with at least one remote peripheral device;

a SCSI bus communications link between the first SCSI adapter and the second SCSI adapter; and

memory resident emulation means in the second computer for emulating a SCSI remote peripheral device for direct access of the SCSI remote peripheral device by the first computer, for emulating a non-SCSI remote peripheral device for direct access of the non-SCSI remote peripheral device by the first computer upon command by the first computer and for synchronizing commands between the first computer and the second computer.

3. The computer network system as defined in claim 2, wherein the first computer and the second computer are BIOS software dependent and the memory resident emulation means enabling the remote peripheral device in the second computer for direct access of the remote peripheral device by the first computer upon command by the first computer provides for proper sharing of any BIOS software interrupt which supports remote peripheral device access by both the first computer and the second computer such that proper hardware and software priority operation is maintained.

4. A computer network system of two computers wherein either one of the two computers accesses a remote peripheral device of the other computer, comprising:

a first computer including a first Small Computer System interface (SCSI) adapter;

a first remote peripheral device, responsive to only one of either a SCSI or a non-SCSI command, connected to and operative by the first computer;

a second computer including a second SCSI adapter;

a second remote peripheral device, responsive to only one of either a SCSI or a non-SCSI command, connected to and operative by the second computer;

a SCSI bus communication link between the first and second SCSI adapters; and

memory resident emulation means in each of the first and second computers, wherein the memory resident emulation means in the second computer is for enabling the second remote peripheral device by generating either a SCSI or a non-SCSI command for direct access of the second remote peripheral device by the first computer upon command by the first computer, and wherein the memory resident emulation means in the first computer is for enabling either a SCSI or a non-SCSI command for direct access of the first remote peripheral device by the second computer upon command by the second computer and for synchronizing the commands from the first computer and the second computer.