right|thumbnail|280px|HARVEST
The IBM 7950, also known as Harvest, was a one-of-a-kind adjunct to the Stretch computer which was installed at the United States National Security Agency (NSA). Built by IBM, it was delivered in 1962 and operated until 1976, when it was decommissioned. Harvest was designed to be used for cryptanalysis.
Development
In April 1958, the final design for the NSA-customized version of IBM's Stretch computer had been approved, and the machine was installed in February 1962. The design engineer was James H. Pomerene, and it was built by IBM in Poughkeepsie, New York. Its electronics (fabricated of the same kind of discrete transistors used for Stretch) were physically about twice as big as the Stretch to which it was attached. Harvest added a small number of instructions to Stretch and could not operate independently.
An evaluation conducted by the NSA found that Harvest was more powerful than the best commercially available machine by a factor of 50 to 200, depending on the task.
Architecture
thumb|280px|A HARVEST tape cartridge.
The equipment added to the Stretch computer consisted of the following special peripherals:
- IBM 7951 — Stream coprocessor
- IBM 7952 — High-performance core storage
- IBM 7955 — Magnetic tape system, also known as TRACTOR
- IBM 7959 — High-speed I/O exchange
- IBM 7302 — Core Storage Memory Unit
With the stream processing unit, Harvest was able to process 3 million characters a second. Harvest was also used for decipherment of solved systems; the report goes on to say that, "Decrypting a large batch of messages in a solved system [is] also being routinely handled by this system".
Harvest remained in use until 1976, having been in operation at the NSA for fourteen years. Part of the reason for its retirement was that some of the mechanical components of TRACTOR had worn beyond use, and there was no practical way to replace them. IBM declined to re-implement the architecture in a more modern technology.
See also
- Cryptanalytic computer