Real Time Computer Complex (RTCC) in the Apollo era

Picture #01

Credit to NASA.

Picture #02

Credit to IBM.

Picture #03

Credit to NASA.

Picture #04

Credit to IBM.

Picture #05

Credit to NASA.

Picture #06

Credit to NASA.

Picture #07

Credit to NASA.

Picture #08

Credit to NASA.

The eight camera viewpoints on the RTCC floor plan.

Floor plan of the Real Time Computer Complex (RTCC)

RTCC floor plan
Five systems can be distinguished (A, B, D, E and F) (letter C was not used).
At the core of each system a mainframe IBM 360 model J75. To this mainframe peripheral systems were connected: additional magnetic core memory units, disk drive units, tape units, line printers, card readers, teletype units, data adapters etc.. In the 1960's this mainframe IBM 360 was one of the most sophisticated computers of its time.

One of those five systems was sufficient to support an Apollo mission. Two of the remaining 4 systems were used as backup.
One mainframe was active, a second mainframe was in dynamic standby and did the same work in parallel with the primary mainframe. A switch to the standby mainframe could be done swiftly in case the primary would fail. A third mainframe was kept in reserve. The two other mainframes were used for simulations, to make preparations for the next upcoming Apollo mission or to process data from the scientific packages of the current mission which were deployed on the lunar surface by the astronauts.

The RTCC was located at the first floor of the Operations Wing of the Mission Control Center (MCC) in Houston)
(This MCC building had 3 wings: the Administrative Wing, the Lobby Wing and the Operations Wing)
The Operations Wing had 3 floors. In 1960's and 1970's there were two Mission Operations and Control Rooms, one MOCR at the second floor and the other MOCR at the third floor).


Typical system configuration of an IBM 360/75 at the RTCC

IBM 360/75 system configuration

Configuration of an IBM 360 / 75 computer as selected by NASA for the Apollo mission support.
Two IBM 2361 Large Core Storage (LCS) as a 4 Mbyte extension of the 4x IBM 2365 256 kbyte Processor Storage (total of 1 Mbyte) as well as a buffering device for retrieving data and programs from the IBM 2314 disk drives.
The IBM 2701 data adapter unit provides a rapid demand response interface to the digital display (D.TV) in the MOCR and the RTCC.
Real time acceptance and transmission of large amounts of data and control information are accomplished through the use of the IBM 2902 Multiplex Line Adapter (MLA).
An IBM 2540 card read / punch, an IBM 1443 line printer, three IBM 1403 printers, two IBM 1052 consoles and eight IBM 2401 tape drive units complete the configuration.

The IBM Storage Channel is an attachment to the IBM 2860-2 Selector Channel. It provides the capability of high-speed data transfer from one location in storage to another location in storage. This transmission between storage areas may be within main storage or between main storage and the large core storage or within large core storage. This storage channel enables swapping of data and programs from low speed storage to high speed main processor storage and vice versa to use the high speed CPU as efficient as possible.


Paper model (1:25) of an IBM 360 Model J75
as used at the Real Time Computer Complex (RTCC)

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Copyright 2020 by Sander Panhuyzen
Comments and questions welcome. All pictures and drawings contained on these pages are the author's, unless otherwise noted. No unauthorized reproduction without permission.