AN/GYK-12
The AN/GYK-12 was a 32-bit minicomputer developed by Litton Industries for the United States Army. The AN/GYK-12 was a militarized version of the L-3050 computer ruggedized for use in the TACFIRE tactical fire direction system. The design dates from the 1960s.[1]
In 1980 the Army introduced the Nebula instruction set architecture (MIL-STD-1862), intended as an upgrade to the AN/GYK-12. Nebula was also a 32-bit architecture with 32-bit addressing mode and instructions optimized for running programs written in Ada.[2]
Description
The basic system consisted of three rack-mounted modules: The CPU, the IOU (Input/Output unit), and the MCMU. Modules were mounted vertically and were 9.32 inches (23.7 cm) wide by 33.75 inches (85.7 cm) high.[3]
The AN/GYK-12 had a 32-bit instruction format and operated on data from one bit to a doubleword (64 bits) in size. Only fixed-point binary arithmetic was provided.
The system could have a maximum of 32768 pages—64 million words—of 2 μs memory (256 MB). Physically memory was divided into banks of 8 KW to minimize memory contention. Logically it was divided into pages of 2 KW each. Access to pages was controlled by 16 Page Control and Address Registers per program level, allowing an individual program to directly address 128 KB at one time.[4]
The AN-GYK-12 CPU featured 64 hardware priority program levels, numbered from 0 (highest) to 63 (lowest). One task could run at each level. Level 0 was reserved for "power off". Level 1 was power-on restart. Level 2 handled hardware and program errors. Level 63 was entered after completion of a boot load. Therefore the system could support a maximum of 60 user tasks. Tasks were scheduled preemptively—a task would run until an error occurred, until it gave up control to another task, or until successful completion of an input/output operation transferred control to the so-called normal program level.
Each task also had a privilege level, which controlled the operations it was allowed to perform. Level '00'b was used for non-privileged programs. Level '01'b programs were semi-privileged. Level '10'b programs were privileged and could execute all instructions and I/O operations. Level '11'b was unused.
References
- ↑ U.S. General Accounting Office. "The Department of Defense's Standardization Program for Military Computers--A More Unified Effort is Needed" (PDF). Retrieved August 25, 2014.
- ↑ Rosenberg, Marcy (Mar 24, 1980). "Army Approves Instruction Set Architecture". Computerworld. Retrieved August 23, 2014.
- ↑ "7021-01-043-0952 (586017-102, AN/GYK-12(V)2) Data". PartTarget.com. Retrieved August 25, 2014.
- ↑ Litton Data Systems (1972). AN/GYK-12 Computer System Principles of Operation Manual (PDF). Fort Belvoir, Virginia: U.S. Army Systems Command. Retrieved August 23, 2014.