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I > IBM  > AN/FSQ-7   


The AN/FSQ-7 was by far the largest computer ever built, and is expected to hold that record. It consisted of two complete Whirlwind II computers installed in a 4-story building (See the impressive diagram in the 'More Pictures' section).

Each AN/FSQ supported more than 100 users. IBM had about 60 employees at each site for round-the-clock maintenance.
Keeping one unit operating and one on hot standby (to allow for switchover when vacuum tubes failed) resulted in better than 99% uptime. The roles of the two units were reversed at regular intervals, allowing diagnostics and maintenance to be carried out on the standby unit.

There were usually several hundred tube failures each day, replaced by workers racing up and down the tube racks with shopping carts full of replacements. Automated tests run by the computer itself would cycle the voltage to the tube racks down and back up to induce marginal tubes to fail early, so that the computer would normally run correctly for the rest of the day. Without this process, the MTBF would have been a few minutes.

By the time SAGE was deployed (22 or 23 stations in the period 1959-1963; sources disagree) it was nearly obsolete, since it was designed to detect bombers, not the new ICBMs. Nevertheless it was operational until 1979, when the ROCC (Regional Operations Control Centers) system took over, using much higher-speed computers. One SAGE station continued operating until 1983. This last unit was donated to the Boston Computing Museum, since relocated to Moffett Field in Mountain View, California. The museum also has a tube panel from the Whirlwind I. Whirlwind II consoles turned up in the TV series Battlestar Galactica.
In spite of its limited military value, the SAGE system served as an excellent prototype for an air-traffic control system. The FAA operated its own AN/FSQ-7 systems for many years after SAGE was shut down. IBM's experience with these systems had a great deal to do with its later success in computer systems, and its dominance of the market for large computers. The IBM 7090 was essentially a solid-state version of the AN/FSQ-7/8. (The 7090 has its own rich history, including hosting the first-ever multiuser APL system.)

• First CRT-based real-time user interface,
• First use of light gun to pick an item on the screen,
• First wide-area modem communications (1300 bps),
• First hot standby system for maximum uptime,
• First ground control of interceptor aircraft,
• The first in line microfilm fast processed 35 mm projection displays, preceding printer/plotters. A screen capture could be displayed within 30 seconds, • First two-pass assembler, permitting symbolic addresses.

Thanks to Edward Cherlin, Simputer Evangelist, for all this information.

The photo (from Mitre) shows the rear panel wiring of FSQ-7 arithmetic element frame.

We need more info about this console ! If you designed, used, or have more info about this system, please send us pictures or anything you might find useful.
Please consider donating your old computer / videogame system to or one of our partners.


I was a first generation USAF "BlueSuit" graduate of the IBM Kingston training program in 1961$my job code was 30551. I was a computer repairman and later computer operator of the Q7 at Duluth Air Defense Sector (DUADS). One topic I have not seen mentioned was the fact that many of the voltages that ran the computer came from motor-generators that were controlled by the computer itself. The pentode tubes were designed so that, when run at lower or higher than normal voltage, they would fail. By this means, the failure rate of 48000 tube system could be acceptably low.

Monday 4th February 2019
Gary Nelson (United States)

I trained as a communications computer systems analyst at Keesler AFB in 1965. We had a field trip to the Q-7 in Montgomery where we each wrote, in JOVIAL, and ran a small program on the backup system. The CRT/light pen programming was fun. For some reason we thought the "NIFA" acronym was hilarious ("not in file area", a flip-flop that was activated by a light reflecting on a piece of aluminum foil glued on the magnetic tape near the end of the reel).

Tuesday 21st August 2018
Michael Yourshaw

Went to Keesler for SAC HQ training, but got assigned to Duluth from 1972 to 1975 Enjoyed the computer maintenance career 30594. Spent 34 years and retired as a Chief.At Duluth the shop manager was a civilian. He used to come at night to drive us crazy installing faults and making us troubleshoot them. Anyone remember 4cv was the main clock.

Wednesday 18th July 2018
Keith Krier (Pittsburgh, PA)


YEAR  1958
CPU  55,000 vacuum tubes in each unit
SPEED  75 KIPS (KiloInstructions Per Second)
RAM  Core 8892-word
ROM  Unknown
GRAPHIC MODES  256 x 256
COLORS  Monochrome
SOUND  Speaker (see the ''Read more'' page)
SIZE / WEIGHT  2000 square meters / 275 tons
I/O PORTS  Tape, punched cards, modem
PRICE  $238 million, printer around $200,000 to $250,000

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