Mainframe Computers

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The Backbone of Big Business

With technology, what you can do influences what you want to do—which gradually expands what you can do.

Businesses in the 1950s increasingly recognized computers’ broad potential. They demanded flexible, large-scale machines able to consolidate varied tasks. The workhorse mainframe computers that met these demands in turn reshaped how businesses operate, increasing centralization and nourishing new demand for powerful mainframes.

IBM 709

The last of IBM's first generation of big scientific vacuum tube computers, this machine was built in 1959. It was the first computer with data channels for IO. This picture shows the Central Processing Unit, which can be opened up like a book to access the wiring. The complete system consists of seven different units including memory, data channels and power supplies plus a card reader, printer and many tape drives. The entire system originally cost $2.5 million. Large corporations, government labs and big universities would have one or two for the entire institution.

The drawings for this machine are fun. Here are some module drawings and diagnostic listings, and here are some drawings for another machine of similar vintage, the IBM 705.
Old IBM software project.

IBM 7094

The IBM 7094 Model I was a middle member of IBM's second generation of scientific computers, built with discrete transistors. The 7094 system is about the same size as the 709 and has the same kinds of peripherals. I also have an IBM 2302 disk drive for the 7094. The disk platters are 24 inches in diameter and the head assembly is positioned with compressed air. It is one of the last models this size and can store 300 MB.
Old IBM software project.

IBM 650

The 650 was the most popular first generation computer. It was small enough that medium size businesses and schools, or individual departments of large institutions could afford one. Here is more about My IBM 650 . Also see the IBM 650 manual project and the IBM pluggable units project in progress. 

IBM 1401

This computer was designed to replace unit record equipment for commercial data processing. It is a character machine which represents numbers as strings of digits delineated by a "word mark" bit. It has an excellent high speed card reader, punch, and line printer and was often used to perform IO for larger machines such as the 709 and 7094.
Old IBM software project.

Other Mainframes
The collection includes an IBM 370/148 CPU and a complete small IBM 4300 system. These represent the fourth generation and beyond and were relatively early members of IBM's current mainframe line. The only non-IBM equipment in the collection that comes close to this category is a Univac 1004, which like the IBM 1401 was designed to replace unit record equipment. It was often used as a remote job entry station for Univac mainframes. There is also a more modern DEC VAX 11/780, which was sometimes considered a super-mini, not quite a mainframe, and the DECSystem/20, which certainly is a mainframe