Marconi Transistorised Automatic Computer

The Marconi Transistorized Automatic Computer was Marconi Company's first computer, designed and manufactured from around 1959. They employed Germanium transistors which by this time were sufficiently reliable with room temperatures kept below about 23 degrees C. The type S3301 was a 20 bit word machine with two Mullard core memory stores providing 4k of 20 bit data, see Ref. 3. Processor status bits were provided with machine instructions being decoded from 6 bits in the current address memory word. Double word data had the MSB designated a sign bit coded as binary fractions ( -1 to +1) for the square root, multiply and divide instructions. The instruction set had the usual functions based on three registers named A, B and D (C was the current address in memory register, M). An additional instruction assisted with checksum calculation for data transferred to and from main data stores (viz. Sperry Rand magnetic drums.).

Applications included marking up radar screens with aircraft info and providing data processing for operators in a Nuclear Power Station. Surviving computers (ex Power Station) are on display at Bletchley Park National Museum of Computing (operational) and Jim Austin's collection near the University of York. Addition manuals and documentation exist at the University of Manchester Computer Museum and the Manchester Rylands library. Marconi went on to develop the Myriad series of computers