Sequence Changes
The TX-2 was an experimental machine and was changed frequently. Hardware elements were added and removed. Using a number of sources of known date, we indicate how the assignments of sequence numbers to hardware changed.
Changes
| Sequence | Date | Reference | Hardware |
|---|---|---|---|
| 00 | 1958 (to 1975+) | TX-2 UH,TM | Startover (i.e. boot-up) |
| 01 to 37 | TX-2 UH,TM | Usable as Index Registers but not as hardware sequences | |
| 40 | 1961 May | TM | Uncertain, but see section 2-7.4 of TM |
| 1975-07-25 | CP91-119 | Main Alarm | |
| 41 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH | In-Out Alarms |
| 42 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH | Trap |
| 43 | 1961 May | TM | Not present |
| 44 | 1961 May | TM | Not present |
| 1975-07-25 | CP91-119 | File Memory | |
| 45 | 1961 May | TM | Not present |
| 1962-06-20 | P91-185 | IBM Magnetic Tape | |
| 1975-07-25 | CP91-119 | FOP (?) Link-Control | |
| 46 | 1961 March | TM | Magnetic Tape (planned, not installed) |
| 1962-06-20 (to 1975+) | P91-185, CP91-119 | Magnetic Tape | |
| 1975-07-25 | CP91-119 | 9-Track Magnetic Tape | |
| 47 | 1961-03-28 (to 1963+) | P91-113, TX-2 UH | Miscellaneous Inputs |
| 50 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH, CP91-119,TM | DATRAC Analog to Digital Numerical Input |
| 51 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH, TM, CP91-119 | Xerox Printer |
| 52 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH, TM, CP91-119 | Photoelecric Tape Reader |
| 53 | 1961 May to 1963-02-28 | P91-214, TM | Apparently not present |
| 1975-07-25 | CP91-119 | IMP (see below; the TX-2 was connected to the ARPAnet some time in or before December 1970) | |
| 54 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH, TM, CP91-119 | Interval Timer |
| 55 | 1961-03-28 (to 1963+) | P91-113, TX-2 UH, TM | Lite Pen |
| 1975-07-25 | CP91-119 | Encoded Interrupt | |
| 56 | 1961-03-28 | P91-113 | Display 2 |
| 1975-07-25 | CP91-119 | IMP (see below) | |
| 57 | 1961 May (to 1963-02-28+) | P91-214, TM | Apparently not present |
| 1975-07-25 | CP91-119 | Low-speed data channel | |
| 60 | 1961-03-28 | P91-113 | Display 1 |
| 1961, November | TX-2 UH | Lite Pen | |
| 1975-07-25 | CP91-119 | Printer/Plotter | |
| 61 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH, CP91-119 | Random Number Generator |
| 62 | 1961 March | TM | Punch 2 (planned, not installed) |
| 1963-02-28 | P91-214 | Punch 2 | |
| 1975-07-25 | CP91-119 | Printer/Plotter | |
| 63 | 1961-03-28 (to 1975+) | P91-113, CP91-119 | Punch 1 |
| 64 | 1961 May (to 1963-02-28+) | P91-214, TM | Apparently not present |
| 1975-07-25 | CP91-119 | Display 4 | |
| 65 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH | Lincoln Writer 1 Input |
| 66 | 1961-03-28 (to 1975+) | P91-113, TX-2 UH | Lincoln Writer 1 Output |
| 67 | 1961 May (to 1963-02-28+) | P91-214, TM | Apparently not present |
| 70 | 1961 May (to 1963-02-28+) | P91-214, TM | Apparently not present |
| 71 | 1961-03-28 | P91-113, TX-2 UH | Lincoln Writer 2 Input |
| 1975-07-25 | CP91-119 | Keyboard Input | |
| 72 | 1961-03-28 | P91-113, TX-2 UH | Lincoln Writer 2 Output |
| 1975-07-25 | CP91-119 | Typewriter Output | |
| 73 | 1961 May (to 1963-02-28+) | P91-214, TM | Apparently not present |
| 1975-07-25 | CP91-119 | BMC?-Control (it’s hard to read the photograph) | |
| 74 | 1961 May (to 1963-02-28+) | P91-214, TM | Plotter (two-coordinate line plotter) |
| 75 | 1961-03-28 | P91-113, TX-2 UH, TM | Miscellaneous Outputs |
| 1975-07-25 | CP91-119 | Apparently not present | |
| 76 | 1961 May (to 1975-07-25+) | P91-214, TM, CP91-119 | Indicator light exists, but this is a software-only sequence |
| 77 | 1961 May (to 1975-07-25+) | P91-214, TM, CP91-119 | Indicator light exists, but this is a software-only sequence |
Hardware
The TX-2 User’s Handbook explains which sequence number is associated with which hardware and explains how to control it. Much of the hardware is also described in the TX-2 Technical Manual.
The copies of the User’s Handbook and Technical Manual which we have date from the period 1961-1963. While we know of hardware which post-dates this period (for example the IMP), we currently have no detailed information about it.
CRT
The Cathode-Ray tube and Lite Pen were necessary for the operation of Sketchpad in 1963. Photographs from 1975 (CP91-71 from 1076-11-06, for example) show that this unit is no longer in Frame 1. The sequence numbers had been re-used for other things (see photograph CP91-119 from 1975-07-25).
IMP
Wes Clark, creator of the TX-2, suggested that computers be interfaced to the ARPAnet by minicomputers at the ARPANET Design Session held by Lawrence G. Roberts at the ARPA IPTO PI meeting in Ann Arbor, Michigan in April 1967. So it seems likely that the IMP listed above as sequences 53 and 56 would be an ARPAnet Interface Message Processor.
The ARPANET Completion Report shows that the TX-2 was connected to the ARPAnet some time before December 1970. It is still shown on the map for June 1975 but is missing from the October 1975 map.
Sources
| Reference | Date | Source document |
|---|---|---|
| P91-113 | 1961-03-28 | Lincoln Lab photograph, P91-113: 03/28/1961, Toggle switch storage panel |
| TX-2 UH | 1961 (July and November) | TX-2 Users Handbook, Chapter 4, “TX-2 In-Out System”; pages are dated individually |
| P91-185 | 1962-06-20 | Lincoln Lab photograph, P91-185: 06/20/1962, Unidentified woman working at TX-2 Control Desk Using the Lincoln Writer |
| P91-214 | 1963-02-28 | Lincoln Lab photograph, P91-214: 02/28/1963, Console Indicator Panel |
| CP91-119 | 1975-07-25 | Lincoln Lab photograph, CP91-119: 07/25/1975, Circuit breaker location panel |
Sources which are not referenced by the table above
These photographs were consistent with the references above but didn’t provide new information.
| Reference | Date | Source document |
|---|---|---|
| P91-211 | 1962-12-08 | Lincoln Lab photograph, P91-211: 12/08/1962, Ivan Sutherland using Sketchpad graphics program at the TX-2 Computer |
| P91-219 | 1963-02-28 | Lincoln Lab photograph, P91-219: 02/28/1963, IN-OUT Buffers and Special Indicators. |
| P91-233 | 1963-12-06 | Lincoln Lab photograph, P91-233: 12/06/1963, Timothy Johnson uses Sketchpad on the TX-2 computer |