|Word Size:||16 bit|
The NORD-20 is functionally identical to the NORD-2B. ND considered the NORD-20 a production version of the NORD-2B. The difference is that the NORD-20 needed only 6 boards instead of 10 for the CPU. (However, unlike the NORD-20 the NORD-2B could be delivered with an I/O system compatible with the NORD-1, or with the same I/O system used by the NORD-20.)
The price for a 4K word system, with teletype and punched tape reader, was only NOK 100,000 in 1971.
- Word length: 16 bits.
- Two sets of registers. An interrupt will switch the CPU to the second set. Interrupt latency is therefore never longer than the time of the slowest instruction.
- Instructions not implemented in hardware are implemented as interrupts. This is used to e.g. handle NORD-1 instructions not implemented in hardware in the NORD-2B/NORD-20, by trapping them and implementing them in software.
- Two program levels: System and user level authorization of instructions.