1. xerox 560 computer system - The UK Mirror Service

6. SYSTEM CONFIGURATION CONTROLPooled resources along with flexible configuration controlprovide a high degree of continuous availability. If aproblem occurs in an individual unit of a resource pool,the system may allow that unit to be isolated with a lossonly in capacity but no loss of functional capability,assuming there is an additional unit of that type in thesystem that can absorb the added load. Specialized unitscan be duplicated (with all units being normally used,where possible) and configuration controls used to divertthe input from one to the other in the event of a failure.Chapter 2 describes the system organization and Chapter 5discusses system operational control. This chapter describesthe Configuration Control Panel (CCP), which servesas the principal element for controlling and modifying theconfiguration of the system.CONFIGURATION CONTROL PANEL (CCP)The CCP provides the capability for enabling and disablingunits in the system. It accomplishes this with centrallylocated manual selection switches used for the followingfunctions:configuration control is designed in a modular manner. Asthe system grows, previously unused rows on the panel canbe used (up to the panel IS maximum of six), and an additionalpanel may be added. Two panels represent the maximumconfiguration for one endbell assembly.Note: The Configuration Control Panel does not contain--- operational controls as the System Control Paneldoes. The CCP switches are initially positionedduring system configuration and are not normallyreposi ti oned duri ng system operati on.CONFIGURATION CONTROL STATUS WORDA program may read settings of the panel switches, type ofunit, and options installed. A READ DIRECT (RD) instructionusing the chassis address of the cluster or unitas an address allows the program to determine the configurationstatus of a particular processor cluster or memoryunit, for example. (The chassis address assignment representsthe chassis ' physical location relative to the endbellassembly.) (See Figure 16.)1. Establish starting addresses for all memory units in thesystem.2. Enable or disable memory ports.3. Enable or disable individual units and clusters.The configuration control status of a panel read by theRD instruction is a 32-bit status word consisting of panelswitch settings and type information. (The RD instruction is descri bed in Chapter 3, .. Control Instructi ons" • )The logic for these program provisions resides in eachunit.4. Control the power throughout the system.The Configuration Control Panel is mounted within the endbellassembly at the end of the row of cabinets containingthe chassis assemblies for the MUs, BP, and other systemcomponents. On the outer surface of the endbell assemblyis the System Control Panel (described and illustrated inChapter 5). Access is gained to the CCP by opening thehinged endbell assembly (see Figure 16).In addition to reading configuration status informationvia a READ DIRECT (RD) instruction in a program, thestatus information may also be obtained by manual switchselection on the System Control Panel; the 32-bit statusword is displayed on a bank of lamp indicators. (SeeChapter 5 for a discussion of the System Control Panelfeatures. )A CCP has six rows of 22 toggle switches and two lamp indicatorseach. A row may control a memory unit, processorcluster, or system control processor. (See Figure 17, andTables 25 and 26.) The active logic assocIated with eachrow of switches and indicators is located within each processorcluster or memory unit itself. Above each row is amarker strip that identifies the function of each switch. TheCONFIGURATION BUSThe configuration bus connects to each processor cl uster andprovides a path for the system control processor to select andread the switch settings on the CCP for the selected unit viaan RD instruction.System Configuration Control 167