ENIAC | December 10, 1945

 

ENIAC (Electronic Numerical Integrator and Computer) was completed in 1945 and is considered the first programmable electronic general-purpose digital computer. While other computers had certain functions, ENIAC was the first to have all capabilities. It is Turing complete and could solve a "wide range of numerical problems" through reprogramming.

Designed by John Mauchly and J. Presper Eckert, ENIAC was developed for the U.S. Army's Ballistic Research Laboratory to compute artillery trajectories. The first program run was actually for the feasibility study of thermonuclear weapons.

ENIAC was first put into operation on December 10, 1945, and officially dedicated on February 15, 1946, at the University of Pennsylvania, costing approximately $487,000 (about $6.9 million in 2023). It was referred to in the press as a "giant brain" and boasted a speed about 1,000 times faster than electromechanical machines.

Officially taken over by the U.S. Army's Ordnance Department in July 1946, ENIAC was relocated to the Aberdeen Proving Ground in Maryland in 1947 and remained operational until 1955.

The design and construction of ENIAC were funded by the Army Ordnance Research and Development Command, led by Brigadier General Glady M. Barnes. The construction contract was signed on June 5, 1943, and work began secretly the following month at the Moore School of Electrical Engineering, University of Pennsylvania, under the project code "Project PX." Key researchers included John Grist Brainerd, and Herman H. Goldstine played a crucial role in securing funding.

ENIAC was a large modular computer made up of individual panels. Twenty of these modules were accumulators, capable of addition and subtraction, and could hold 10-digit decimal numbers. Data was transferred among these devices through multiple general-purpose buses. To achieve high speed, the panels transmitted, received, calculated, and stored numbers without moving parts.

The core of ENIAC’s versatility was its branching capability, which could trigger various tasks based on the sign of calculated results.

By the time ENIAC ceased operation in 1956, it contained 18,000 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000 capacitors, and about 5,000,000 hand-soldered joints. Weighing over 30 tons (27 metric tons), it was approximately 8 feet (2 meters) high, 3 feet (1 meter) deep, and 100 feet (30 meters) long, occupying 300 square feet (28 m²) and consuming 150 kW of electricity. Input was through an IBM card reader, and output used IBM punch cards, which could also be processed offline by IBM accounting machines. Initially lacking a memory system, ENIAC used punch cards for external memory storage, later adding a 100-word magnetic core memory in 1953.

ENIAC utilized a 10-digit ring counter for number storage, requiring 36 vacuum tubes per number. Arithmetic operations were performed by "counting" pulses with the ring counter, generating carry pulses when wrapping around.

With 20 accumulators, ENIAC could perform 5,000 simple additions or subtractions per second using 10's complement. Multiple accumulators could operate in parallel for greater speed. It could connect accumulators for double precision, but connecting more than three was not feasible due to timing issues.

ENIAC could perform a maximum of 385 multiplications per second using four accumulators controlled by a special multiplier unit, and 40 divisions or three square roots per second using five accumulators with a special divider/square root calculator unit.

Its remaining nine units included starting/stopping devices, a cycling unit for synchronization, a master programmer for loop sequencing, a reader for the IBM punch card reader, a printer for the IBM punch, constant transmitters, and three function tables.

The basic machine cycle was 200 microseconds, allowing 5,000 cycles per second for 10-digit numbers. Multiplying two 10-digit numbers took 14 cycles, or 2,800 microseconds, resulting in a speed of about 357 per second. Division and square root calculations took 13(d+1) cycles, where d is the number of digits in the result.

ENIAC could process around 500 FLOPS, comparable to modern supercomputers’ petascale and exascale performance.

Reliability was a concern as ENIAC used common octal vacuum tubes. The decimal accumulators were constructed with 6SN7 flip-flops, while various tubes performed logical functions. Multiple vacuum tubes failed daily, with an average downtime of two days per failure. By 1954, ENIAC achieved a record 116 hours of continuous operation, nearing five days.