TX-0
From Computer History Wiki
The TX-0 was a transistor computer (reportedly the first ever built), at the MIT Lincoln laboratory. Predecessor to the TX-2 and an influence on the PDP-1 design. It was in some sense a successor to the Memory Test Computer, itself a spin-off of the pioneering Whirlwind.
Registers
These are the registers in the original design. Later updates changed some register widths and added registers.
| Name | Size (bits) | Meaning |
|---|---|---|
| AC | 18 | Accumulator |
| MBR | 18 | Memory buffer register |
| MAR | 16 | Memory address register |
| PC | 16 | Program counter |
| IR | 2 | Instruction register |
| LR | 18 | Live register |
| TBR | 18 | Toggle switch buffer register |
| TAC | 18 | Toggle switch accumulator |
Test mode
The console has a switch to set test mode in which operations are taken from the TBR. The operations are similar to regular instructions, but with a different interpretation:
| TBR 0-1 | Instruction | Meaning |
|---|---|---|
| 00 | STO x | Store TAC in memory location x. |
| 01 | ADD x | Add memory location x to AC. (Check MBR to examine.) |
| 10 | TRN x | Change to normal mode and start running at location x. |
| 11 | OPR x | Execute the instruction. |
External links
- TX-0 - documents at Bitsavers
- RLE-TR-627 TX-0 Computer History
- MIT TX-0 Computer
- C. Gordon Bell, Gerald Butler, Robert Gray, John E. Mcnamara, Donald Vonada, and Ronald Wilson, The PDP-1 and Other 18-Bit Computers, in C. Gordon Bell, J. Craig Mudge, John. E. McNamara, Computer Engineering: A DEC View of Hardware Systems Design, Digital Press, Bedford, 1978 - Some material on the TX-0, and also covers its descendants (including the PDP-1)
- The LINC Was Early and Small - lengthy personal memoir by Wesley Clark; it also covers the TX-0
