NORD-12

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General Characteristics

The NORD-12 computer system is a compact mini-computer system with an unusually large instruction set.

The NORD-12 belongs to the NORD-10 family of 16-bit computers where program compatibility with the NORD-10 is assured by the fact that both the instruction set and the Read Only Memory which controls the instruction execution is common to both the NORD-10 and the NORD-12. For readers familiar with the NORD-10, we recommend you read Appendix C which lists all differences between NORD-12 and NORD-10.

A basic instruction set is common to all NORD-12 machines, and this set is highly optimized to produce effective code; hardware floating point arithmetic is standard as are the instructions to manipulate individual bits at high speed.

The register structure and addressing scheme facilitate the processing of structured data with high efficiency.

The NORD-12 is micro-programmed, and all NORD-12 instructions are executed by means of a micro-program located in a very fast (65 ns) read only memory. Micro-programming gives the NORD-12 computer flexibility and a very large growth potential. New instructions may be optimized for a particular use.

NORD-12 provides up to 1024 customer-specified instructions. These instructions are micro-programmed in a programmable read-only memory, which is added onto the standard read-only memory.

Micro-programming in NORD-12 is also used to control the operator's panel and to perform operator communication between the operator and the console Teletype or display.

Bootstrap loaders both for character-oriented devices and mass storage devices are also controlled by a micro-program.

The NORD-12 uses MOS type memories with memory size from 4K to 64K words; memory increment size is 4K. Memory parity is an option in which case the word-length is 18 bits with one parity bit for each 8-bit byte.

Another option is a power fail/auto restart system which also provides 30 minutes of memory stand-by power.

The NORD-12 standard processor executes at a speed of 490 ns for each micro-instruction. This manual gives complete timing figures for all instructions.

The input/output and interrupt systems of NORD-12 are designed for ease of use and very high speed. NORD-12 has 16 program levels each with its own set of registers, making possible a complete context switching from one program level to another in only 2.0 microseconds. In addition 2048 vectored priority input/output interrupts are standard. [1]

Differences between NORD-10 and NORD-12

This appendix is provided for those comparing NORD-10 with NORD-12.[2]

  1. Maximum memory size of the NORD-12 is 64K words. The Memory Management System option is not available for the NORD-12. With this option the maximum memory size for NORD-10 is 256K words.
  2. The speed of the NORD-10 is 300 ns per micro-instruction for NORD-12 it is 500 ns per micro-instruction. This gives a 5/3 ratio for floating point, for all other instructions consult the NORD-10 and NORD-12 Reference Manuals.
  3. Internal hardware error interrupts are not connected to level 14 on the NORD-12, and there is no IIE (Internal Interrupt Enable) register and no IIC (Internal Interrupt Code). However, on the NORD-12 it is possible to hardwire interrupts to level 14.
  4. NORD-12 is only available with dynamic MOS memories (4096 bit/chip), while NORD-10 is offered with a range of different memories.
  5. The rounding algorithm for floating point differs between NORD-10 and NORD-12. On NORD-12 there is no TG (Rounding) flip-flop in the Status Register (bit 1 in Status on NORD-1), and for NORD-12 all floating point results are truncated. On the NORD-10 the least significant bit in the result is forced to one if the result could not be exactly represented. For both the NORD-10 and NORD-12 all integers up to 232-1 will be exactly represented in floating point format, and all results to this limit will also be exact.
  6. Only NORD-10 may have a NORD-1 Input/Output Channel as option.
  7. The Memory Parity systems differs between NORD-10 and NORD-12. On NORD-10 TRA instructions are used for reading memory parity error information, on NORD-12 the parity mechanism is an Input/Output device which plugs into an I/O Slot. For both NORD-10 and NORD-12 Memory Parity is an option.
  8. On NORD-10 the Bus Transceiver or Bus Extender is standard, this is an option on NORD-12.

Sources

  1. ↑ NORD-12 Reference Manual, Introduction
  2. ↑ NORD-12 Reference Manual, Appendix C
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