Browse Prior Art Database

Degraded Mode of a File Subsystem Processor

IP.com Disclosure Number: IPCOM000042529D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Carter, DW: AUTHOR [+3]

Abstract

A file subsystem processor (FSP) enhances system performance. However, on rare occasions, this processor will be inoperative. The system is still available when the FSP is inoperative because the disk and diskette will remain running. The present arrangement enables the system to remain operative even when the file subsystem becomes inoperative. The code for the disk and diskette can operate in either the central processing unit (CPU) or the FSP. At system initial program load (IPL) time, the FSP is in the Data Path C mode (see figure). This enables microcode to be brought directly from disk to the CPU. The CPU now runs under this microcode and begins to IPL the system. At the time of FSP IPL, a status check is made to determine if the FSP hardware is functional.

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Degraded Mode of a File Subsystem Processor

A file subsystem processor (FSP) enhances system performance. However, on rare occasions, this processor will be inoperative. The system is still available when the FSP is inoperative because the disk and diskette will remain running. The present arrangement enables the system to remain operative even when the file subsystem becomes inoperative. The code for the disk and diskette can operate in either the central processing unit (CPU) or the FSP. At system initial program load (IPL) time, the FSP is in the Data Path C mode (see figure). This enables microcode to be brought directly from disk to the CPU. The CPU now runs under this microcode and begins to IPL the system. At the time of FSP IPL, a status check is made to determine if the FSP hardware is functional. If not so, the FSP remains in the data path C mode with disk and diskette under CPU control. If so, the FSP IPL is attempted through data path A, where the microcode is transferred from the CPU to the FSP. If this is not successful, the FSP is set back to the data path C mode with disk and diskette remaining under CPU control, where full disk and diskette support is available. If IPL is successful, disk, diskette, and tape I/O devices are under the FSP control. When disk, diskette, and tape run under the FSP, which is connected to the system, the FSP has three data paths, i.e., data path A -- FSP to/from CPU transfers; data path B -- FSP to/from I/O device tran...