IBM Mainframe - Smaller Machines

Smaller Machines

Prior to System/360, IBM also sold computers smaller in scale that were not considered mainframes, though they were still bulky and expensive by modern standards. These included:

• IBM 650 (vacuum tube logic, decimal architecture, business and scientific)
• IBM 305 RAMAC (vacuum tube logic, first computer with disk storage; see: Early IBM disk storage)
• IBM 1400 series (business data processing; very successful and many 1400 peripherals were used with the 360s)
• IBM 1620 (decimal architecture, engineering, scientific, and education)

IBM had difficulty getting customers to upgrade from the smaller machines to the mainframes because so much software had to be rewritten. The 7010 was introduced in 1962 as a mainframe-sized 1410. The later Systems 360 and 370 could emulate the 1400 machines. A desk size machine with a different instruction set, the IBM 1130, was released concurrently with the System/360 to address the niche occupied by the 1620. It used the same EBCDIC character encoding as the 360 and was mostly programmed in Fortran, which was relatively easy to adapt to larger machines when necessary.

Midrange computer is a designation used by IBM for a class of computer systems which fall in between mainframes and microcomputers.