The UNIVAC 418 was a transistorized, 18-bit word core memory machine made by Sperry Univac. The name came from its 4-microsecond memory cycle time and 18-bit word. The assembly language for this class of computers was TRIM III and ART418. Over the three different models, more than 392 systems were manufactured. It evolved from the Control Unit Tester, a device used in the factory to test peripherals for larger systems.
k - Designator used for channel number, shift count, etc.
Numbers were represented in ones' complement, single and double precision. The TRIM assembly source code used octal numbers as opposed to more common hexadecimal because the 18-bit words are evenly divisible by 3, but not by 4. The machine had the following addressable registers:
A - Register composed of:
*AU - Register
*AL - Register
ICR - Register, also designated the "B-register"
SR - Register, a paging register allowing direct access to memory banks other than the executing bank
The 418-I was also available in a militarized version as the UNIVAC 1218. It was almost 6 feet tall and weighed. It required both 115VAC, 1-phase, 60 Hz and 115VAC, 3-phase, 400 Hz power.
UNIVAC 418-II
The first UNIVAC 418-II was delivered in November 1964. It was available with 4,096 to 65,536 words of memory. Memory cycle time was reduced to 2 microseconds. The militarized version was called the UNIVAC 1219 It was part of the Navy's Mk 76 missile fire control system, used to control the AN/SPG-55radar system.
UNIVAC 418-III
The first UNIVAC 418-III was delivered in 1969. It was available with 32,768 to 131,072 words of memory. Memory cycle time was reduced to 750 nanoseconds. New instructions were added for floating-point arithmetic, binary-to-decimal and decimal-to-binary conversions, and block transfers up to 64 words. The SR register was expanded to 6 bits. The 418-III had two unique hardware features which enabled it to handle continuously high speed serial character streams. One was called the buffer overflow interrupt and the other hardware buffer chaining. By the 1990s, all the 418 hardware was gone, but the California Department of Water Resources was still running 418 emulation on a UNIVAC 1100/60.
