UNIVAC 1108
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The UNIVAC 1108 was the second member of Sperry Rand's UNIVAC 1100 series of computers, introduced in 1964. Integrated circuits replaced the thin film memory that the UNIVAC 1107 used for register storage. Smaller and faster cores were used for main memory.
In addition to faster components, two significant design improvements were incorporated: base registers and additional hardware instructions. The two 18-bit base registers (one for instruction storage and one for data storage) permitted dynamic relocation: as a program got swapped in and out of main memory, its instructions and data could be placed anywhere each time it got reloaded. The additional hardware instructions included double precision arithmetic, double word load, store, and comparison instructions. The processor could have up to 16 input/output channels for peripherals.
Just as the first UNIVAC 1108 systems were being delivered in 1965, Sperry Rand announced the UNIVAC 1108 II (also known as the UNIVAC 1108A) which had support for multiprocessing: up to three CPUs, four memory banks totaling 262,144 words, and two independent programmable input/output controllers (IOCs). With everything busy, five activities could be going on at the same moment: three programs running in the CPUs and two input/output processes in the IOCs. One more instruction was incorporated: test-and-set, to provide for synchronization between the CPUs.
Although a 1964 internal study indicated only about 43 might sell, in all, 296 processors were produced.
When Sperry Rand replaced the core memory with semiconductor memory, the same machine was released as the UNIVAC 1100/20. In this new naming convention, the final digit represented the number of CPUs (called CAUs) in the system.
