Category Archives: 1956

The Bendix G-15 was a vacuum tube computer produced by the Bendix Corporation in 1956. It was unique for its time because of its size and pricing compared to other computers of the era. At only 5 x 3 feet and a cost of about $60,000 for a working model, it was an affordable computer and was marketed to the scientific and industrial sectors. Although it’s designer had worked with Alan Turing and the ACE and SWAC computers, it was phased out when Control Data Corporation took over the company’s computer division in 1963.

A serial-architecture machine like the ACE, it used a magnetic drum but was unable to retain memory when it was shut down. It had over 180 vacuum tube packs and included peripherals like a typewriter, photoelectric tape reader, and a high speed paper tape punch. Around 400 were produced and it was used heavily in civil engineering.

From an IBM press release, 1956 | IBM History.

The 650 RAMAC and 305 RAMAC both utilize the magnetic disk memory device announced as experimental by IBM a year ago. Both machines are the first of a planned line of equipment designed for high-volume, in-line processing of business data. Transactions are processed continuously, as they occur, instead of being held until a group is accumulated, sorted and batch processed. In a single step, all records affected by a transaction will be immediately adjusted to account for the change.

The 650 RAMAC combines the IBM 650 Magnetic Drum Data Processing Machine with a series of disk memory units which are capable of storing a total of 24-million digits. The 305 RAMAC is an entirely new machine which contains its own input and output devices and processing unit as well as a built-in 5-million-digit disk memory. Both machines operate according to a program of electronically stored instructions.

An advanced feature of the new continuous accounting machines is the method by which the memory may be interrogated. With the 650 RAMAC, typewriter operators at remote inquiry stations may “ask” the machine for any of the data in the vast memory. Instants later the answer — perhaps a sales total or an inventory figure — appears on the typewriter. The same remote machine may be used to introduce information directly to the memory. The 305 RAMAC may be interrogated in a similar manner directly from the machine’s console.

The monthly charge for 305 RAMAC is $3,200. Prices on the 650 RAMAC will be announced at a later date. Deliveries on both will start in mid-1957 although several test 305 RAMAC’s are being delivered this year.

The TX-0 (Transistorized eXperimental computer 0) was built to aid in the testing of it’s big brother, the TX-2, and many of the features used in the TX-2 were first tested on the TX-0. This was one of the reasons why the TX-0 was originally equipped with 64Kword memory (each word being 18 bits). When work on the TX-0 began, it was not clear if such large magnetic core memories could be built.

The memory was stripped down to 4Kword memory when it was delivered to RLE but was later upgraded to 8Kword. The 18 bit words used 16 bits to address the original 64Kword memory leaving two bits for instructions. When it became apparent that it would never be equipped with its original 64Kword memory, the three unused address bits were used to add a set of new instructions.