Browse Prior Art Database

Expandable, Fault Tolerant Read Only Storage Apparatus

IP.com Disclosure Number: IPCOM000110408D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 105K

Publishing Venue

IBM

Related People

Shippy, DJ: AUTHOR

Abstract

This article provides an expandable Read-Only Storage (ROS) access scheme which uses a common system I/O bus instead of a dedicated ROS address bus. Furthermore, it provides a fault-tolerant system which has the capability to switch between multiple ROS modules.

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Expandable, Fault Tolerant Read Only Storage Apparatus

       This article provides an expandable Read-Only Storage
(ROS) access scheme which uses a common system I/O bus instead of a
dedicated ROS address bus. Furthermore, it provides a fault-tolerant
system which has the capability to switch between multiple ROS
modules.

      Fig. 1 shows a system diagram of a processor consisting of a
Icache Unit (ICU), Fixed-Point Unit (FXU), Floating-Point Unit (FPU),
Dcache Unit (DCU), and a Storage Control Unit (SCU).  The processor
chips are packaged on a single Multi-Chip Module (MCM) substrate.
The functional units not on the MCM are a central MEMORY, ROS, and
I/O control units (IOCs).  The IOCs provide the I/O bus interface to
I/O devices.  They move data from an asynchronous bus, such as the
MICRO CHANNEL, to processor bus speeds on the System I/O bus (SIO
bus).  The SIO bus is a two-word address/data bus which has the dual
purpose of interfacing with the I/O chips as well as providing the
address bus for the ROS modules.

      The ROS access mechanism is located in the SCU chip (Fig. 2).
The SCU generates the ROS address and ROS data controls to the DCU
which indicate when to load the ROS data.  The SCU also controls
which ROS module to access during a ROS access.  For loading purposes
the ROS modules are evenly distributed on the two words of the SIO
bus.  One ROS module contains all of the instructions and data needed
for system bring-up. Two ROS modules are sh...