The CERN SPS and LEP PowerPC project is aimed at introducing a new generation of PowerPC VMEbus processor modules running the LynxOS real-time operating system. This new generation of front end computers using the state-of-the-art microprocessor technology will first replace the obsolete Xenix PC based systems (about 140 installations) successfully used since 1988 to control the LEP accelerator. The major issues addressed in the scope of this large scale project are the technical specification for the new PowerPC technology, the re-engineering aspects, the interfaces with other CERN wide projects, and the set up of a development environment. This project offers also support for other major SPS and LEP projects interested in the PowerPC microprocessor technology

Van den Eynden, M

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12ptThe New Generation of PowerPC VMEbus Front End Computers forthe CERN SPS and LEP Accelerators Control SystemM.Vanden EyndenSL Controls GroupEuropean Laboratory for Particle PhysicsCH1211 Geneva 23 - SwitzerlandAbstractThe CERN SPS and LEP PowerPC project is aimedat introducing a new generation of PowerPC VMEbus pro-cessor modules running the LynxOS real-time operatingsystem.This new generation of front end computers using thestate-of-the-art microprocessor technology will rst replacethe obsolete Xenix PC based systems (about 140 installa-tions) successfully used since 1988 to control the LEP ac-celerator.The major issues addressed in the scope of this large scaleproject are the technical specication for the new PowerPCtechnology, the re-engineering aspects, the interfaces withother CERN wide projects, and the set up of a develop-ment environment.This project oers also support for other major SPS andLEP projects interested in the PowerPC microprocessortechnology.INTRODUCTIONThe mission of the European Laboratory for ParticlePhysics is pure science - particle physics - probing the in-nermost constituents of matter to nd out how our worldand the whole of the Univers works.To do this, it operates a number of particle accelerators,the largest of which is the LEP electron-positron collider.Beams of electrons and their antimatter counter-parts,positrons, are circulating in a 27 kilometer undergroundring at the speed of light and collided together.As shown in Figure 1, a chain of accelerators, including theSuper Proton Synchrotron(SPS), provides beams for LEP.The LEP machine consists of various equipment installedin the 27 km ring tunnel and in 8 surface buildings, theirassociated pits and underground areas.The SPS and LEP Control System extends from a centralcontrol room to all the surface buildings and undergroundareas in order to provide command and aquisition facilitiesfor the collider and the particle beams.Figure 1: Schematic of CERN's intricate particlebeam network, showing the 27-kilometer LEP ring,the 7-kilometer SPS ring, and their injectorsTHE SPS AND LEP CONTROL SYSTEMARCHITECTUREAs shown in Figure 2, the architecture of the SPS andLEP control system [1] is modeled on three layers : theControl Room Layer, the Front End Computing Layer,and the Equipment Control Layer.THE CONTROL ROOM LAYERThe Control Room Layer is composed by modernUNIX workstations, servers and X-Terminals. HumanComputer Interfaces are developed using an X-Windowand OSF/Motif User Interface Management System.Several other UNIX servers are used for le storage, forpublic displays, for the management of the alarms, andfor an ORACLE on-line relational database.Figure 2: The SPS and LEP Control SystemTHE FRONT END LAYERThe Front End Computing Layer consists of FrontEnd process computers (FEs) based on PCs and VMEbuscrates. Their main function is to provide a uniforminterface to the equipment as seen from the workstationsand act as data concentrators for equipment interfacedvia various ledbuses.The task assignment between FEs is made on geograhicalor functional criteria. The communication between theHuman Computer Interfaces (HCI) running in the SPSand LEP control room and the FEs is achieved throughRemote Procedure Calls (RPC) or direct TCP/IP socketconnections.The current computer installation for these two layers isthe following : 150 OS/9 VMEbus Systems 110 LynxOS 2.2.0 80486 PC systems 45 LynxOS 2.1.0 VMEbus 680x0 systems 150 Xenix 2.3.1 80386 PC systems 7 DEC workstations 30 Hewlett Packard 700 series workstations 100 X-TerminalsNEW FRONT ENDS ARCHITECTUREAs shown in Figure 3, the new generation of FEswill consist of a standard VMEbus crate, a VMEbusprocessor module based on the PowerPC family, variouseldbus controller modules and equipment dedicated I/OFigure 3: The new PowerPC LynxOS Front EndsFigure 4: Connection to 100 MHz FDDI Backbonemodules.LynxOS is the chosen operating system for the new FEs.The LynxOS installation will also include : host based TCP/IP networking software for Ethernet; Network File System (NFS), client and server; NetBoot rmware for bootstrap loading LynxOS sys-tems over the network; LynxOS drivers for VMEbus, Ethernet, SCSI-II, andRAMDISK.The connection of the FEs to the local Ethernet segmentwill be done directly from the processor module. As shownin Figure 4, connections to the future FDDI networkwill be done via a separate Data-Link module tightlycoupled to the processor via a dedicated PCI interfacecard, conforming to the PMC specication.SOFTWARE DEVELOPMENT ENVIRONMENTAs the new generation of FEs will be diskless, boot-strap load les are prepared on development systems,stored on a boot server and loaded into target systemsover the network.Application programs will be compiled, linked anddebugged with the GNU software (gcc, g++, gdb).This development activity will be possible either fromPowerPC LynxOS native development systems, or byusing cross-development facilities running on an IBM AIXworkstation. This second option oers to the developersthe comfort and performance of a classical workstationdevelopment environment. The binaries produced on theIBM AIX workstation will then be stored in a repositoryfrom where they will be loaded onto the target systems.THE EQUIPMENT LAYERThe Equipment Control Layer consists of EquipmentControl Assemblies (ECAs) connected to the FEs viavarious equipment eldbuses (MIL-1553, GPIB, BITBUS,JBUS) or via RS232/422 links.The accelerator equipment is distributed in undergroundhalls and in surface buildings.Network communication is made by local Ethernetsegments bridged to large Token-Rings, one for the LEPgeneral services linking all the surface buildings andothers for the accelerators. These Token-Rings are nowbeing replaced by 100 Mbit FDDI backbones to cover theentire CERN site. The data distribution is based on theTCP/IP protocol suite and the network management isachieved with SNMP.PROJECT MOTIVATIONSThe PC Xenix installation has been intensively used since1988 to control most of the LEP accelerator services (i.e.vacuum system, tunnel cooling and ventilation, electrivity,water distribution, magnets, and so forth).These computers run on a 24h/day and 365day/year ba-sis and the experience has proved that their reliability andmodularity is not as good as the one obtained with indus-trial VME crates.The second important motivation is the desire to use theNetwork File System (NFS) and the LynxOS operatingsystem in all our FEs to simplify our maintenance eort(i.e today several generic software packages like the oneused for Remote Procedure Call have to be maintained ontoo many dierent operating systems).But the interest in VMEbus and PowerPC microprocessoris not only limited to these aspects, several major reju-venation projects dealing with the SPS power converters(ROCS project) and the LEP Beam Synchronisation Tim-ing (BST project) have high performance requirements andwill take benet from the new PowerPC microprocessortechnology.PROJECT OBJECTIVESThe two objectives of the project are : the replacement of the operational PC Xenix systems(70 installations) by VMEbus PowerPC 603/604 sys-tems running the LynxOS operating system. The oldPC Xenix consoles will be replaced by X-Terminalsconnected to the Hewlett Packard workstations; the setup of a development environment for the SPSand LEP VMEbus PowerPC users. This environmentshall provide the necessary tools to migrate the exist-ing PC Xenix operational software (more than 100software modules) and to perform low level develop-ments at the operating system level (i.e drivers).TECHNOLOGICAL CHOICESThe use of the VMEbus was dictated by the large invest-ment already made by the SPS and LEP controls andequipment groups in this technology. PCs and VMEbussystems running LynxOS have replaced a variety of olderhardware and software in the SPS and LEP acceleratorscontrol system including, in particular, obsolete NORD100minicomputers during the SPS controls upgrade project in1994. The choice of the PowerPC microprocessor cameafter a world wide market investigation in August 1994.Most of commercial oers were based on the new Pow-erPC 603 and/or 604 microprocessor technology.The nal technical specication for the VMEbus processormodules [2] was published in September 1994 and the tar-get systems were ordered in December 1994. LynxOS hasbeen selected as the unique operating system for all FEs.Its kernel allows drivers to be dynamically installed anduninstalled while the system is running. Most interruptprocessing is delegated to system threads to insure prompthandling of device interrupts and consistent scheduling ofactivities according to their priority. No local disk norgraphics will be used.PROJECT MANAGEMENTPRELIMINARY CONSIDERATIONSAt the beginning of the project it was decided touse mechanisms to monitor progress, generate milestonesand reduce the risk linked to the technology involved inthe project.Various aspects like : the project scale (140 Xenix systems) the new PowerPC technology the dierent categories of users (application programsdevelopers but also low level operating system special-ists) the interface with major projects like ROCS and BST the re-engineering aspects the operational contraints (continuous LEP accelera-tor operation required)led us to use software and hardware engineering standardsto manage the project. The IEEE software engineeringstandards [3] and the European Space Agency (ESA)PPS-05 standards [4] were used to address both technicaland managerial project issues.PROJECT LIFECYCLEThe project organizational structure, the organiza-tional boundaries and interfaces, and the individualresponsibilities are specied in the project managementplan (PMP) document.The project lifecycle is divided in six phases : the userrequirements phase, the system requirements phase, thearchitectural design phase, the detailed design phase,the transfer in operation phase, and the operation andmaintenance phase.USER REQUIREMENTS PHASEProbably the most crucial phase of the entire project.The objectives of this phase are to identify all entitiesinvolved in the project (this activity was mandatoryaccording to the lack of documentation concerning theexisting software modules) and capture the requirementsfor the future operational and development systems.Several technological evolutions (i.e. cross-developmentenvironments) as well as the experience gained during thepast seven years with the Xenix systems raised new userrequirements. After being published, the User Require-ments Document (URD) was reviewed and accepted asthe baseline document for the next project phases.PROJECT PROTOTYPING ACTIVITYAccording to the technical issues involved in theproject, it was decided during the system requirementsphase of the project to spend time on prototyping.As shown in Figure 5, this prototyping activity is aimedat : improving the denition of the user requirements.Building a prototype may lead to new requirementsor to the discovery of incomplete or contradictory re-quirements;Figure 5: Project Prototyping Phase gaining knowledge about the technical feasibility, thesystem requirements, and any aspect related to theoperation of such a system; producing a model for the nal development andoperational systems.PROJECT DESIGN PHASESThe architectural and detailed design phases areaimed at dening a collection of software and hardwarecomponents and their interfaces and building the nalsystem. The installation of the development environment,the writing of the System User Manual (SUM), and themigration of the Xenix software modules will take placeduring the detailed design phase.CONCLUSIONSAt present we are tackling the prototyping phase of theproject. The acceptance tests for the rst PowerPC 603processor board has been successful and the bulk deliv-ery will start before autumn 1995 and will continue duringrst quarter 1996. The prototyping activities will be de-veloped in two directions : several target systems will beinstalled in parallel to the existing Xenix PCs to checktheir behaviour under operational conditions, and at thesame time developers will try to migrate some of the Xenixsoftware modules using either the new cross-developmentenvironment or native LynxOS development systems, de-pending on the nature of that software.The architectural and detailed design phases will start be-fore December 1995 and the time table for the transfer inoperation has still to be discussed. It is expected to gain afactor of ten to twenty in computing power comparing thenew FEs to the old Xenix FEs.I. References[1] Interfacing Industrial Equipment to CERN's Acceler-ators and Services Control SystemP.Anderssen, P.Charrue, R.Lauckner, P.Lienard,R.Rausch, M.Tyrrell, M.Vanden Eynden[2] Specication for the Supply of PowerPC VMEbusProcessor Modules Running LynxOS Real-Time Op-erating System SoftwareCERN SL/Tech.Spec.94-05-CO[3] Software Engineering - IEEE Standards CollectionInstitute of Electrical and Electronics Engineers, Inc[4] Software Engineering Standards - Prentice HallC.Mazza, J.Fairclough, B.Melton, D.De Pablo,A.Scheer, R.Stevens

The new generation of PowerPC VMEbus front end computers for the CERN SPS and LEP accelerators control system

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