IBM 650

The IBM 650 was IBM's first commercial business computer, a 2-address, bi-quinary coded decimal[?] computer, with memory on a rotating drum, introduced in 1954. It was specifically designed for users of existing IBM unit record equipment[?] upgrading from Calculating Punches (e.g., IBM 604) to computers.

The 650 system consisted of three cabinets:

• Console Unit
• Power Unit
• Card Reader/Punch Unit (Type 533[?])

The rotating drum memory provided 2000 10-digit words of memory, but was slow as a word could not be accessed until it passed under the read/write heads (avg. access time 2.5mS). An optional Magnetic Core unit providing 60 10-digit words, was introduced later to provide a little fast memory (access time 96uS).