PDP-1-X

The PDP-1-X was a heavily modified PDP-1 created at MIT's RLE.

Notable differences are:

• the addition of operating modes to the CPU (to support time-sharing): 'TS Off', 'TS Debug', 'Exec' (used for the kernel), and 'User';
• additional instructions;
• the addition of an index register;
• an I/O bus for connection of peripherals.

External links

• RLE PDP-1 - Original RLE PDP-1 documents
  • PDP-1 Timesharing System Memos
  • Modes, Registers, New Instructions, and Traps and Interrupts in the PDP-1-X
• Machine readable copies of paper tapes and DECtapes from MIT:
  • MIT RLE PDP1X
  • DEC PDP1 paper tape images