System and method for providing uniform access to a SCSI bus by

Details System and method for providing uniform access to a SCSI bus by System and method for providing uniform access to a SCSI bus by

1994-11-30

1997-03-18

Harvey, Jack B.

395856, 395859, G06F 1336

Patent

active

056130767

ABSTRACT:
A host device SCSI bus controller in SCSI bus system for uniformly distributing I/O tasks, thereby providing all devices equal access to a SCSI bus without decreasing the overall utilization of the bus. The controller prevents system errors from occurring due to I/O tasks not being transmitted when the connectivity of the bus is fully utilized and the bus is operating near saturation. The controller alters the host device performance during the arbitration phase by replacing the single occurrence of the SCSI standard specified arbitration phase with multiple arbitration phases. In the multiple arbitration phases the controller does not assert the host device ID until a user determined time after the completion of the SCSI standard specified arbitration phase. When the host device has an I/O command to transmit, SCSI bus controller executes a first arbitration phase, wherein it does not assert the host device ID unless there are no reselecting target devices and not until a user defined time after the SCSI standard specified arbitration delay has completed. This gives a reselecting target device the opportunity to gain control over the SCSI bus. Then, if there are additional reselecting target devices on the SCSI bus, the SCSI bus controller performs additional arbitration phases until the bus is free. At that time, the SCSI bus controller issues the pending I/O command. By delaying the assertion of the host device ID during repeated arbitration phases, the SCSI bus controller enables the remaining target devices the opportunity to sequentially gain control over the SCSI bus. The SCSI bus controller therefore allows all target devices to reselect the host device to complete previously issued I/O tasks prior to the host device issuing additional I/O commands. The SCSI bus controller allows for an exception when a host I/O command is delayed to such an extent that further delay will cause a system error. Under such conditions, the SCSI bus controller asserts the host ID during the next standard arbitration phase. The host will then win arbitration and transmit the critical I/O command.

REFERENCES:
patent: 4821170 (1989-04-01), Bernick et al.
patent: 4864291 (1989-09-01), Korpi
patent: 5008808 (1991-04-01), Fries et al.
patent: 5034881 (1991-07-01), Hoashi et al.
patent: 5081578 (1992-01-01), Davis
patent: 5204951 (1993-04-01), Keener et al.
patent: 5247622 (1993-09-01), Choi
patent: 5274783 (1993-12-01), House et al.
patent: 5283872 (1994-02-01), Ohnishi
patent: 5287463 (1994-02-01), Frame et al.
patent: 5289580 (1994-02-01), Latif et al.
patent: 5301332 (1994-04-01), Dukes
patent: 5313588 (1994-05-01), Nagashige et al.
patent: 5333277 (1994-07-01), Searls
patent: 5377331 (1994-12-01), Drerup et al.
patent: 5471618 (1995-11-01), Isfeld
patent: 5475850 (1995-12-01), Kahn

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