UNIVAC 1100/2200 series

The UNIVAC 1100/2200 series is a series of compatible 36-bit computer systems, beginning with the UNIVAC 1107 in 1962, initially made by Sperry Rand. The series continues to be supported today by Unisys Corporation as the ClearPath IX.

Architecture

Data Formats

Fixed-point either integer or fraction
- Whole word - 36 bit (one's complement)
- Half word - two 18 bit fields per word (unsigned or one's complement)
- Third word - three 12 bit fields per word (one's complement)
- Quarter word - four 9 bit fields per word (unsigned)
- Sixth word - six 6 bit fields per word (unsigned)
Floating point
- Single precision - 36 bits: 1 sign bit, 8 bit characteristic, 27 bit mantissa
- Double precision - 72 bits: 1 sign bit, 11 bit characteristic, 60 bit mantissa
Alphanumeric
- Fieldata - 6 bits
- ASCII - 9 bits

Instruction Format

Instructions are 36 bits long with the following fields:

f ( 6 bits) - function designator (opcode),

j ( 4 bits) - partial word designator, J-register designator, or minor function designator,

a ( 4 bits) - register (A, X, or R) designator or I/O designator,

x ( 4 bits) - index register (X) designator,

h ( 1 bit ) - index register increment designator,

i ( 1 bit ) - indirect address designator,

u (16 bits) - address or operand designator.

Address	Register	Contents
000	Unused	Unused
001	X1	Increment	Modifier
...	...	Increment	Modifier
013	X11	Increment	Modifier
014	X12/A0	Overlap (X or A)
...	...	Overlap (X or A)
017	X15/A3	Overlap (X or A)
020	A4	Accumulator
...	...	Accumulator
033	A15	Accumulator
034	A15+1	Unassigned (A)
...	...	Unassigned (A)
037	A15+4	Unassigned (A)
...	Executive	Protected Executive
101	R1	Special (R)
...	...	Special (R)
117	R15	Special (R)
...	Executive	Protected Executive
177	Executive	Protected Executive

Registers

The 128 registers of the high speed "general register stack", map to the current data space in main storage starting at memory address zero. These registers include both user and executive copies of the A, X, R, and J registers and many special function executive registers.

The table on the right shows the addresses (in octal) of the user registers.

There are 15 index registers (X1 ... X15), 16 accumulators (A0 ... A15), and 15 special function user registers (R1 .. R15). The 4 J registers and 3 "staging registers" are uses of some of the special function R registers.

One interesting feature is that the last 4 index registers (X12 ... X15) and the first 4 accumulators (A0 ... A3) overlap, allowing data to be interpreted either way in these registers. This also results in 4 unassigned accumulators (A15+1 ... A15+4) that can only be accessed by their memory address (double word instructions on A15 do operate on A15+1).

Early UNIVAC machines with 110x numbers, but not in the 1100 series

These machines had different architectures and word sizes and were not compatible with each other. They all used vacuum tubes and many used drum memory as their main memory.

UNIVAC 1101 introduced in 1950.
UNIVAC 1102 introduced in 1953.
UNIVAC 1103 introduced in 1953.
UNIVAC 1104 introduced in 1957.
UNIVAC 1105 introduced in 1958.

UNIVAC 1100 series

These machines had a common architecture and word size. They all used transistorized electronics and integrated circuits. Early machines used core memory until that was replaced with semiconductor memory in 1975.