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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]
"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 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.
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 ...
A single program deck, with individual subroutines marked. The markings show the effects of editing, as cards are replaced or reordered. Many early programming languages, including FORTRAN, COBOL and the various IBM assembler languages, used only the first 72 columns of a card – a tradition that traces back to the IBM 711 card reader used on the IBM 704/709/7090/7094 series (especially the ...
In computer hardware, a word mark or flag is a bit in each memory location on some early variable word length computers (e.g., IBM 1401, 1410, 1620) used to mark the end of a word. [1] Sometimes the actual bit used as a word mark on a given machine is not called word mark , but has a different name (e.g., flag on the IBM 1620, because on this ...