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WEIZAC (Weizmann Automatic Computer)

Overview

The WEIZAC was the first computer in Israel and one of the first large-scale, stored-program electronic computers in the world. Built at the Weizmann Institute of Science in Rehovot during 1954–1955, it was based on the IAS architecture. The project was driven by Chaim L. Pekeris’s desire to solve Laplace’s tidal equations and was personally supported by John von Neumann. Despite severe parts shortages in the young state of Israel, the team improvised brilliantly – sourcing copper strips from a bicycle repair shop among other expedients. The WEIZAC operated from late 1955 until December 29, 1963, and was recognized as an IEEE Milestone in 2006.

Technical Specifications

Specification Detail
Word length 40 bits
Instruction format 20-bit (8-bit instruction code + 12-bit addressing)
Initial memory 1024 words on magnetic drum
Memory upgrade 4096-word magnetic-core module (later)
Further expansion (1961) Two additional 4096-word modules
Vacuum tubes ~2000 (some sources cite ~3000 including all subsystems)
I/O Punched paper tape; magnetic tape added in 1958
Architecture Based on IAS design; four times the memory of the original IAS machine (after upgrades)
Operational period Late 1955 – December 29, 1963
Total service hours ~46000 hours

Design and Construction History

Origins and Motivation

The WEIZAC project was initiated by Chaim Leib Pekeris, who had worked at the Institute for Advanced Study in Princeton during the time von Neumann’s IAS machine was being designed. Chaim Weizmann, Israel’s first president, had asked Pekeris to establish the Department of Applied Mathematics at the Weizmann Institute. Pekeris wanted a computer to solve Laplace’s tidal equations for the Earth’s oceans.

Von Neumann’s Personal Involvement

Von Neumann actively supported the project. When questioned about the utility of such a machine for “that tiny country,” he responded: “Don’t worry about that problem. If nobody else uses the computer, Pekeris will use it full time!”

The Estrin Team

In 1952, Gerald Estrin, a research engineer from the von Neumann project at IAS (where he had worked from 1950 to 1956), was chosen to lead the construction. He came to Israel in 1954 along with his wife Thelma Estrin, an electrical engineer who also contributed to the project. The core team included technician Micha Kedem and mathematician/programmer Aviezri Fraenkel (later a distinguished professor).

Construction Challenges

The challenges were immense. Upon arrival, the Estrins discovered that there were no parts or tools – from vacuum tubes to soldering irons – available in Israel, and no trained staff.

  • Parts sourcing: The Weizmann Institute worked with a company called Landseas Import-Export (offices in New York and Tel Aviv) to purchase equipment. Components began arriving at Israel’s ports of Haifa and Tel Aviv in June 1954.
  • The bicycle repair shop: Some components, notably thin copper strips, came from a local bicycle-part shop. Some assembly work was done in a bicycle repair shop due to lack of proper laboratory facilities. This became one of the most celebrated anecdotes in Israeli computing history.
  • Budget: $50000, which represented 20% of the Weizmann Institute’s total budget – an extraordinary commitment for the young nation.

Timeline

  • 1947: Von Neumann supports the concept
  • 1952: Gerald Estrin selected to lead the project
  • 1954: Estrins arrive in Israel; equipment procurement begins
  • June 1954: Components begin arriving at Israeli ports
  • Late 1955: First calculation performed (October 1955 per some sources)
  • December 29, 1963: WEIZAC retired
  • 1963: Replaced by a CDC 1604A; simultaneously, construction began on the locally designed GOLEM (based on ILLIAC II architecture)

What Science Was Done on It

Tidal Calculations and the Amphidromic Point Discovery

Pekeris’s driving motivation was realized magnificently. Using WEIZAC, he solved Laplace’s equations for the M2 tide in the world’s oceans, accounting for the structure of continents and coastlines. The calculation predicted the existence of a previously unknown amphidromic point in the South Atlantic – a location where the tide does not change. Measurements later performed by the British Royal Navy confirmed the existence and location of this point. This was one of the great early triumphs of computational science.

Programmer Yigal Accad converted Pekeris’s equations into machine code for the calculations.

Atomic Spectroscopy

WEIZAC numerically calculated the eigenvalues of a two-electron atom quantum system. The results were later independently verified by Brookhaven National Laboratory.

Other Scientific Applications

  • Earthquake studies
  • X-ray crystallography
  • Random walk methods
  • Numerical analysis
  • Defense Ministry calculations

Notable Anecdotes

  • Von Neumann’s quip: “Don’t worry about that problem. If nobody else uses the computer, Pekeris will use it full time!”
  • Bicycle shop ingenuity: The sourcing of precision copper strips from a bicycle repair shop became a symbol of Israeli improvisation (later celebrated in the national narrative as characteristic of the “start-up nation” spirit).
  • First computer in the Middle East: WEIZAC was the first electronic computer in the entire Middle East.
  • Gerald Estrin’s later career: After returning from Israel, Estrin joined UCLA in 1956, where he developed the concept of reconfigurable computing. His doctoral students included Vint Cerf (a father of the internet) and David Patterson.

Decommissioning and Current Status

  • December 29, 1963: WEIZAC was retired after approximately 46000 hours of service.
  • December 5, 2006: WEIZAC was recognized by the IEEE as a Milestone in the history of electrical engineering and computing. The team who built it was awarded the “WEIZAC Medal.”
  • A section of WEIZAC has been on display at the Weizmann Institute since at least 2007.

Sources

  • “WEIZAC,” Wikipedia. https://en.wikipedia.org/wiki/WEIZAC — Accessed: 2026-04-02
  • “Milestones: WEIZAC Computer, 1955,” Engineering and Technology History Wiki (IEEE). https://ethw.org/Milestones:WEIZAC_Computer,_1955 — Accessed: 2026-04-02
  • “How Israel’s First Computer Was Built in a Bike-Repair Shop,” Weizmann USA. https://www.weizmann-usa.org/news-media/in-the-news/how-israel-s-first-computer-was-built-in-a-bike-repair-shop/ — Accessed: 2026-04-02
  • “Remembering WEIZAC: The Beginning of Computing in Israel,” Weizmann USA. https://www.weizmann-usa.org/news-media/in-the-news/remembering-weizac-the-beginning-of-computing-in-israel/ — Accessed: 2026-04-02
  • “Gerald Estrin,” Wikipedia. https://en.wikipedia.org/wiki/Gerald_Estrin — Accessed: 2026-04-02
  • “Thelma Estrin,” Wikipedia. https://en.wikipedia.org/wiki/Thelma_Estrin — Accessed: 2026-04-02
  • “Israel computer pioneer Gerald Estrin dies at 90,” Times of Israel. https://www.timesofisrael.com/israel-computer-pioneer-gerald-estrin-dies-at-90/ — Accessed: 2026-04-02
  • “WEIZAC and GOLEM: The Start-Up Nation’s Earliest Computers,” National Library of Israel. https://blog.nli.org.il/en/hoi_weizac/ — Accessed: 2026-04-02
  • “Tide and Prejudice,” Davidson Institute / Weizmann Institute. https://davidson.weizmann.ac.il/en/online/sciencepanorama/tide-and-prejudice — Accessed: 2026-04-02