8/12/2023 0 Comments Ge tube clock radio![]() ![]() Similarly, indirect addressing became more common in the second generation, either in conjunction with index registers or instead of them. Although index registers were introduced in the first generation under the name B-line, their use became much more common in the second generation. In the second generation there was considerable development of new address modes, including truncated addressing on, e.g., the Philco TRANSAC S-2000, the UNIVAC III, and automatic index register incrementing on, e.g., the RCA 601, UNIVAC 1107, GE 635. ![]() On some computers, e.g., PDP-6, the same registers served as accumulators and index registers, making them an early example of general-purpose registers. In the second generation, it became common for computers to have multiple addressable accumulators. In the first generation, word-oriented computers typically had a single accumulator and an extension, referred to as, e.g., Upper and Lower Accumulator, Accumulator and Multiplier-Quotient (MQ) register. Magnetic thin film and rod memory were used on some second-generation machines, but advances in core technology meant they remained niche players until semiconductor memory displaced both core and thin film. The second generation saw both simpler, e.g., channels on the CDC 6000 series had no DMA, and more sophisticated designs, e.g., the 7909 on the IBM 7090 had limited computational, conditional branching and interrupt system.īy 1960, magnetic core was the dominant memory technology, although there were still some new machines using drums and delay lines during the 1960s. Typically binary computers with word size up to 36 bits had one instruction per word, binary computers with 48 bits per word had two instructions per word and the CDC 60-bit machines could have two, three, or four instructions per word, depending on the instruction mix the Burroughs B5000, B6500/B7500 and B8500 lines are notable exceptions to this.įirst-generation computers with data channels (I/O channels) had a basic DMA interface to the channel cable. All but the smallest machines had asynchronous I/O channels and interrupts. The most common word sizes for binary mainframes were 36 and 48 bits, although entry-level and midrange machines used smaller words, e.g., 12 bits, 18 bits, 24 bits, 30 bits. With the advent of the IBM System/360, two's complement became the norm for new product lines. The second-generation computer architectures initially varied they included character-based decimal computers, sign-magnitude decimal computers with a 10-digit word, sign-magnitude binary computers, and ones' complement binary computers, although Philco, RCA, and Honeywell, for example, had some computers that were character-based binary computers and Digital Equipment Corporation (DEC) and Philco, for example, had two's complement computers. Meanwhile, second-generation computers were also being developed in the USSR as, e.g., the Razdan family of general-purpose digital computers created at the Yerevan Computer Research and Development Institute. Also, towards the end of the second generation Digital Equipment Corporation (DEC) was a serious contender in the small and medium machine marketplace. However, some smaller companies made significant contributions.
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