Honeywell 316 - Hardware Description

Hardware Description

The 316 succeeded the earlier DDP-516 model and was promoted by Honeywell as suitable for industrial process control, data acquisition systems, and as a communications concentrator and processor. The computer processor was made of small-scale integration DTL monolithic integrated circuits. Most parts of the system operated at 2.5 MHz but some elements were clocked at 5 MHz. The computer was a bitwise-parallel 2's complement system with 16 bit word length. The instruction set was a single-address type with an index register. Initially released with a capacity of 4096 through 16,385 words of memory, later expansion options allowed increasing memory space to 32,768 words. Memory cycle time was 1.6 microseconds; an integer register-to-register "add" instruction took 3.2 microseconds. An optional hardware extension was available to implement arithmetic on single- and double-precision floating point values; the basic processor relied on software to carry out floating point calculations.

The programmer's model of the H/316 consisted of the following registers:

• The 16-bit A register was the primary arithmetic and logic accumulator
• the 16-bit B register was used for double-length arithmetic operations
• the program counter was 16 bits long and contained the address of the next instruction.
• A carry flag indicated arithmetic overflow and was used for multiple-precision calculation.
• A 16-bit X index register was also provided for modification of the address of operands.

The instruction set had 72 arithmetic, logic, I/O and program flow control instructions.

Input/output instructions used the A register and separate input and output 16-bit buses. A 10 bit I/O control bus, consisting of 6 bits of device address information and 4 bits of function selection, was used. The basic processor had a single interrupt signal line, but an option provided up to 48 interrupts.

In addition to a front panel display of lights and toggle switches, the system supported different types of input/output devices. One or more Teletype Model 33 ASR teleprinters could be used as console I/O devices, and to load and store data to paper tape. Card readers and punches could also be included. The Honeywell family of peripherals included magnetic tape, fixed disk with a capacity of 3.6 million bytes, and the drum stored 196 thousand bytes.

A rack-mounted configuration weighed around 150 pounds and used 475 watts of power. Honeywell advertised the system as the first minicomputer selling for less than $10,000.

The Honeywell 316 has the distinction of being the first computer displayed at a computer show with semiconductor RAM memory. In 1972, a Honeywell 316 was displayed with a semiconductor RAM memory board (they used core memory previously). It was never placed into production, as DTL was too power hungry to survive much longer. Honeywell knew that the same technology that enabled the production of RAM spelled the end of DTL computers, but wanted to show that the company was cutting edge.

• Front panel of H316 in a desktop case

• Rack-mounted version of H316