IBM 9020
| Company type | Computer system |
|---|---|
| Industry | Air traffic control, Computer hardware |
| Founded | Late 1960s |
| Headquarters | United States |
| Products | Multiprocessor computer systems (9020A, 9020D, 9020E) |
The IBM 9020 was a multiprocessor adaptation of the IBM System/360 computer, specifically designed to support the U.S. FAA's Air Traffic Control operations.[1] Beginning in the late 1960s, it was installed across the FAA's 20 en route Air Route Traffic Control Centers (ARTCCs),[2] and was also utilized by the U.K. CAA at its London facility.[3] The 9020A variant was derived from the S/360-50, whereas the 9020D incorporated two or three S/360-65 processors for handling flight and radar data, complemented by S/360-50 units dedicated to input/output tasks.[2]
There were three principal versions: 9020A CCC (Central Computer Complex), 9020D CCC, and 9020E DCC (Display Channel Complex). The 9020A CCC interfaced with display complexes not produced by IBM, while the 9020D CCC supported connections to either non-IBM displays or IBM's own 9020E DCC. Both the 9020A and 9020D processed flight and radar information but depended on attached display complexes to deliver plan view displays (PVDs) for air traffic controllers. Within the United States, the Raytheon 730 Computer Display Channel (CDC) was employed, capable of driving up to 60 PVDs; however, five ARTCCs requiring greater capacity utilized the IBM DCC, which could support up to 90 PVDs. In contrast, the U.K. implemented the Plessey Processed Radar Display System (PRDS).[4]
The air traffic control applications operated on a customized version of OS/360 MVT, referred to as OS/9020 or simply the “Monitor.” This system provided essential services such as communications management, storage handling, timing coordination, scheduling, and data recording.[5] Developed using JOVIAL, a programming language well-suited for extensive table and linked list operations integral to the system,[6] various support utilities and compilers also ran under OS/9020.[5]
Initially, three CCC models were proposed based on flight plan (FP) capacity: 9020A (up to 325 FPs), 9020B (200 FPs), and 9020C (100 FPs). Ultimately, only the 9020A and the higher-capacity 9020D (capable of managing up to 650 FPs) were produced.
Each FAA ARTCC featured a System Maintenance Monitor Console (SMMC), which consolidated status indicators for the installed 9020 systems along with related subsystems such as environmental controls and communication equipment.
A complete CCC/DCC installation could include as many as twelve IBM S/360 mainframes; however, not every ARTCC operated at this maximum scale. The London centre in the U.K. utilized a "Triplex" configuration of the 9020D system comprising six IBM S/360 units—three S/360-65 processors paired with three S/360-50 processors.
In addition to operational ARTCC locations, four other sites hosted systems dedicated to support, development, or training purposes: The FAA's National Aviation Facilities Experimental Center (NAFEC) maintained various configurations; the FAA Academy operated training systems; a simplex 9020D supported the CAA's London operations; and Raytheon conducted tests of its display technology using a 9020A.
At Jacksonville ARTCC, an initial deployment of a 9020A system was later replaced by a more advanced 9020D. The decommissioned 9020A was repurposed as the Central Flow Control Computer at the FAA's Washington-based ATCSCC, where it provided digital connectivity to command functions until it was superseded by an IBM 4341 in 1984.
On June 9, 1977, an agreement between the FAA and Iran's Civil Aviation Organization outlined plans for installing a $29 million package including both a 9020D and a 9020E as part of a broader $272 million contract aimed at upgrading Iran's National Airspace System.[7] Delivery was ultimately suspended due to the Iranian Islamic Revolution in 1979.
| ARTCC | CCC | Display |
|---|---|---|
| Albuquerque | IBM 9020A | Raytheon 730 |
| Atlanta | IBM 9020D | Raytheon 730 |
| Boston | IBM 9020A | Raytheon 730 |
| Chicago | IBM 9020D | IBM 9020E |
| Cleveland | IBM 9020D | IBM 9020E |
| Denver | IBM 9020A | Raytheon 730 |
| Fort Worth | IBM 9020D | IBM 9020E |
| Houston | IBM 9020A | Raytheon 730 |
| Indianapolis | IBM 9020D | Raytheon 730 |
| Jacksonville | IBM 9020D | Raytheon 730 |
| Kansas City | IBM 9020D | Raytheon 730 |
| Los Angeles | IBM 9020D | Raytheon 730 |
| Memphis | IBM 9020A | Raytheon 730 |
| Miami | IBM 9020A | Raytheon 730 |
| Minneapolis | IBM 9020A | Raytheon 730 |
| New York City | IBM 9020D | IBM 9020E |
| Oakland | IBM 9020A | Raytheon 730 |
| Salt Lake City | IBM 9020A | Raytheon 730 |
| Seattle | IBM 9020A | Raytheon 730 |
| Washington DC | IBM 9020D | IBM 9020E |
| London (United Kingdom) | IBM 9020D | Plessey PRDS |
System longevity and subsequent replacements
The 9020A and 9020D systems remained in service across North America until 1989, at which point they were succeeded by IBM 3083 BX1 mainframes as part of the FAA's HOST Computer System (HCS) modernization effort. Later, these 3083 units were replaced by IBM 9672 RA4 parallel processing servers during the FAA's Host and Oceanic Computer System Replacement (HOCSR) completed in 1999. This upgrade addressed concerns—likely without basis—regarding the IBM 3083’s microcode compatibility with the Year 2000 issue. Initially, the FAA’s original assembly language code was executed on the 9672s through System/360 emulation. Due to the failure of the FAA’s Advanced Automation System (AAS) initiative, the 9020E Display Channel Complexes continued to operate well into the 1990s.
In the United Kingdom, the Civil Aviation Authority (CAA)/NATS utilized a 9020D system running NAS from 1974 until 1990, after which NAS was migrated to an IBM 4381 system designated as the Host Computer System (HCS). This setup retained the System/360 Peripheral Adapter Modules (PAMs) originally part of the 9020D. The three PAM units (IBM 7289s) were retired on November 27, 1997, when replaced by SPRINT.
Configuration specifics of the UK 9020 system
From 1974 through 1990, the IBM 9020D operated at London Air Traffic Control Centre, RAF West Drayton, providing support for UK air traffic controllers.
The UK implemented a triplex configuration of the 9020D comprising three S/360 Model 65 and three S/360 Model 50 processors sharing discs, tape drives, printers, and card readers. Among these processors, three functioned as Compute Elements (CE) running flight data processing software within a real-time multiprocessor framework; the other three served as Input Output Compute Elements (IOCE), managing I/O channel programs and radar input. Typically, two CEs and two IOCEs were active during operations, while one CE and one IOCE remained on standby as automatic backups in case of hardware failure. Additionally, a simplex system was employed for testing and development purposes.
The NAS software operated within a memory footprint of approximately 2.5 MB, with spare storage elements automatically activated if necessary.
The UK NAS software encompassed five principal functions: 1) Route processing—converting flight plans into navigational fixes annotated with estimated times, altitudes, and assigned control sectors. 2) Strip posting—generating printed flight strips ahead of sector entry to assist controllers in maintaining aircraft separation. 3) Radar processing—transforming data from ten radar sources into coordinates using stereographic projection to ensure optimal coverage. 4) Correlation—linking radar beacon codes with flight plans to monitor flights and inform controllers of any schedule deviations. 5) Coordination—electronically transferring flights between neighboring countries via a straightforward protocol confirming position, altitude, and timing.
Flight plan databases were saved every thirty seconds; if a failure occurred, a restart sequence was initiated involving memory dumps for diagnostic purposes and database recovery within two to ten seconds. Subsequent improvements quarantined flight plans that caused repeated restarts.
The software package included comprehensive tools for building, debugging, analyzing, testing, and patching. To conserve runtime resources, geographic airspace data and peripheral addresses were pre-processed offline into a pre-populated database during system construction.
During the late 1980s, the UK’s 9020D developed a reputation for unreliability due to experiencing two failures within one year; however, investigations revealed these incidents resulted from defective UPS units rather than faults in the computer itself. At decommissioning, it was determined that the system could have functioned on lower frequency power with minor modifications.
In 1990, NAS software was migrated onto IBM System/370 Model 4381 processors equipped with DASD and tape storage arranged in a main-standby configuration monitored by heartbeat signals. When standby failure was detected, automatic failover took place involving peripheral switching and flight plan database reconstruction. This rehosted environment no longer utilized a multiprocessor architecture.
Sources
- IBM FAA 360/65-9020 display, Stanford University Computer History Museum – images depicting the recycling process of the 9020E
- Switches set to 'off' signify the conclusion of an era, UK Civil Aviation Authority staff newspaper – coverage on the final deactivation of PAM
Further reading
- Central Flow Control Computer Program Specifications, Volumes I, III, IV, and V
- Central Flow Control Software Design Document, Volumes I and II
- IBM Systems Journal, Volume 6, Issue 2 (1967) – detailed examination of the IBM 9020 system
External links
- Documentation for IBM 9020 available at Bitsavers
- Principles of Operation manual for IBM 9020D and 9020E
- ↑ IBM Systems Journal, Volume 6, Issue 2, 1967.
- ↑ 2.0 2.1 Cite error: Invalid
<ref>tag; no text was provided for refs namedanalysis - ↑ Gibson, Gary, 2020
- ↑ New Scientist, 1980
- ↑ 5.0 5.1 Cite error: Invalid
<ref>tag; no text was provided for refs namedspec-volume-iii - ↑ FAA reports
- ↑ IRAN - Aviation: Technical Assistance