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IBM 1620 data processing machine with IBM 1627 plotter, on display at the 1962 Seattle World's Fair. The IBM 1620 was a model of scientific minicomputer produced by IBM.It was announced on October 21, 1959, [1] and was then marketed as an inexpensive scientific computer. [2]
The IBM 1620, the Data General Nova, the HP 2100 series, and the NAR 2 each have such a multi-level memory indirect, and could enter such an infinite address calculation loop. The memory indirect addressing mode on the Nova influenced the invention of indirect threaded code .
In the 360/65 and 360/67, IBM introduced a concept known as prefixing. [2] Prefixing is a level of address translation that applies to addresses in real mode and to addresses generated by dynamic address translation, using a unique prefix assigned to each CPU in a multiprocessor system.
Early computers that were exclusively decimal include the ENIAC, IBM NORC, IBM 650, IBM 1620, IBM 7070, UNIVAC Solid State 80.In these machines, the basic unit of data was the decimal digit, encoded in one of several schemes, including binary-coded decimal (BCD), bi-quinary and two-out-of-five code.
"One method of designing a slave memory for instructions is as follows. Suppose that the main memory has 64 K words (where K = 1024) and, therefore, 16 address bits, and that the slave memory has 32 words and, therefore, 5 address bits." [48] IBM 1620 CPU Model 1 (a decimal machine) System Reference Library, dated 19 July 1965, states:
The DEC VT100, a widely emulated computer terminal IBM 2741, a widely emulated computer terminal in the 1960s and 1970s (keyboard/printer) A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing [1] data from, a computer or a computing system. [2]
These machines are often quite slow because of this. For example, instruction fetches on an IBM 1620 Model I take 8 cycles (160 μs) just to read the 12 digits of the instruction (the Model II reduced this to 6 cycles, or 4 cycles if the instruction did not need both address fields). Instruction execution takes a variable number of cycles ...
An early widespread implementation was available via the IBM 1620 of 1959–1970. The 1620 was a decimal-digit machine which used discrete transistors, yet it had hardware (that used lookup tables) to perform integer arithmetic on digit strings of a length that could be from two to whatever memory was available. For floating-point arithmetic ...