The history of computing hardware starting at 1960 is marked by the conversion from vacuum tube to solid-state devices such as transistors and then integrated circuit (IC) chips. Around 1953 to 1959, discrete transistors started being considered sufficiently reliable and economical that they made further vacuum tube computers uncompetitive. Metal–oxide–semiconductor (MOS) large-scale integration (LSI) technology subsequently led to the development of semiconductor memory in the mid-to-late 1960s and then the microprocessor in the early 1970s. This led to primary computer memory moving away from magnetic-core memory devices to solid-state static and dynamic semiconductor memory, which greatly reduced the cost, size, and power consumption of computers. These advances led to the miniaturized personal computer (PC) in the 1970s, starting with home computers and desktop computers, followed by laptops and then mobile computers over the next several decades.

Second generation

For the purposes of this article, the term "second generation" refers to computers using discrete transistors, even when the vendors referred to them as "third-generation". By 1960 transistorized computers were replacing vacuum tube computers, offering lower cost, higher speeds, and reduced power consumption. The marketplace was dominated by IBM and the seven dwarfs:

IBM The BUNCH Burroughs UNIVAC NCR Control Data Corporation (CDC) Honeywell General Electric RCA.

Some examples of 1960s second generation computers from those vendors are:

the IBM 1401, the IBM 7090/7094, and the IBM System/360; the Burroughs 5000 series; the UNIVAC 1107; the NCR 315; the CDC 1604 and the CDC 3000 series; the Honeywell 200, Honeywell 400, and Honeywell 800; the GE-400 series and the GE-600 series; the RCA 301, 3301, 501, and the Spectra 70 series.

However, some smaller companies made significant contributions. Also, towards the end of the second generation Digital Equipment Corporation (DEC) was a serious contender in the small and medium machine marketplace.

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.

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. With the advent of the IBM System/360, two's complement became the norm for new product lines.

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. All but the smallest machines had asynchronous I/O channels and interrupts. 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.

First-generation computers with data channels (I/O channels) had a basic DMA interface to the channel cable. 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.

By 1960, magnetic core was the dominant memory technology, although there were still some new machines using drums and delay lines during the 1960s.

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.

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. In the second generation, it became common for computers to have multiple addressable accumulators. 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 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, and the GE-600 series. Although index registers were introduced in the first generation under the name B-line, their use became much more common in the second generation. Similarly, indirect addressing became more common in the second generation, either in conjunction with index registers or instead of them. While first-generation computers typically had a small number of index registers or none, several lines of second-generation computers had large numbers of index registers, e.g., Atlas, Bendix G-20, IBM 7070.

The first generation had pioneered the use of special facilities for calling subroutines, e.g., TSX on the IBM 709. In the second generation, such facilities were ubiquitous; some examples are: Automatically record the next sequential instruction (NSI) in a register for all or most successful branch instructions The Jump Address (JA) Register on the Philco TRANSAC S-2000 The Sequence History (SH) and Cosequence History (CSH) registers on the Honeywell 800 The B register on an IBM 1401 with the indexing feature Automatically record the NSI at a standard memory location following all or most successful branches Store P (STP) locations on RCA 301, 3301 and 501 STICC on the RCA 601 is relative to the lower bound register Call instructions that save the NSI in the first word of the subroutine Return Jump (RJ) on the UNIVAC 1107 Return Jump (RJ) on CDC 3600 and CDC 6000 series Jump to Subroutine (JSR) on the DEC PDP-6 and PDP-10 Call instructions that save the NSI in an implicit or explicit register Branch and Load Location in Index Word (BLX) on the IBM 7070 Transfer and Set indeX (TSX) on the IBM 7090 Jump and Save PC (JSP) on the DEC PDP-6 and PDP-10 Transfer and Set Xn (TSXn) on the GE-600 series Branch and Link (BAL) on the IBM System/360 Call instructions that use an index register as a stack pointer and push return information onto the stack Push jump (PUSHJ) on the DEC PDP-6 Implicit call with return information pushed onto the stack Program descriptors on the Burroughs B5000 line Program descriptors on the Burroughs B6500 line

The second generation saw the introduction of features intended to support multiprogramming and multiprocessor configurations, including master/slave (supervisor/problem) mode, storage protection keys, limit registers, protection associated with address translation, and atomic instructions.

Supercomputers

Second generation supercomputers were substantially faster than most contemporary mainframes. Some of the technologies developed in order to achieve the desired performance are now used in commodity computers.

Third generation

The mass increase in the use of computers accelerated with Third Generation computers starting around 1966 in the commercial market. These generally relied on early (sub-1000 transistor) integrated circuit technology. The third generation ends with the microprocessor-based fourth generation.

In 1958, Jack Kilby at Texas Instruments invented the hybrid integrated circuit (hybrid IC), which had external wire connections, making it difficult to mass-produce. In 1959, Robert Noyce at Fairchild Semiconductor invented the monolithic integrated circuit (IC) chip. It was made of silicon, whereas Kilby's chip was made of germanium. The basis for Noyce's monolithic IC was Fairchild's planar process, which allowed integrated circuits to be laid out using the same principles as those of printed circuits. The planar process was developed by Noyce's colleague Jean Hoerni in early 1959, based on the silicon surface passivation and thermal oxidation processes developed by Carl Frosch and Lincoln Derrick in 1955 and 1957.

Computers using IC chips began to appear in the early 1960s. For example, the 1961 ASD Semiconductor-Network Computer (Molecular Electronic Computer), the first monolithic integrated circuit general purpose computer (built for demonstration purposes, programmed to simulate a desk calculator) was built by Texas Instruments for the US Air Force.

Some of their early uses were in embedded systems, notably used by NASA for the Apollo Guidance Computer, by the military in the LGM-30 Minuteman intercontinental ballistic missile, the Honeywell ALERT airborne computer, Alt URL and in the Central Air Data Computer used for flight control in the US Navy's F-14A Tomcat fighter jet.

An early commercial use was the 1965 SDS 92. IBM first used ICs in computers for the logic of the System/360 Model 85 shipped in 1969 and then made extensive use of ICs in its System/370 which began shipment in 1971.

The integrated circuit enabled the development of much smaller computers. The minicomputer was a significant innovation in the 1960s and 1970s. It brought computing power to more people, not only through more convenient physical size but also through broadening the computer vendor field. Digital Equipment Corporation became the number two computer company behind IBM with their popular PDP and VAX computer systems. Smaller, affordable hardware also brought about the development of important new operating systems such as Unix.

In November 1966, Hewlett-Packard introduced the 2116A minicomputer, one of the first commercial 16-bit computers. It used CTμL (Complementary Transistor MicroLogic) in integrated circuits from Fairchild Semiconductor. Hewlett-Packard followed this with similar 16-bit computers, such as the 2115A in 1967, the 2114A in 1968, and others.

In 1969, Data General introduced the Nova and shipped a total of 50,000 at $8,000 each. The popularity of 16-bit computers, such as the Hewlett-Packard 21xx series and the Data General Nova, led the way toward word lengths that were multiples of the 8-bit byte. The Nova was first to employ medium-scale integration (MSI) circuits from Fairchild Semiconductor, with subsequent models using large-scale integrated (LSI) circuits. Also notable was that the entire central processor was contained on one 15-inch printed circuit board.

Large mainframe computers used ICs to increase storage and processing abilities. The 1965 IBM System/360 mainframe computer family are sometimes called third-generation computers; however, their logic consisted primarily of SLT hybrid circuits, which contained discrete transistors and diodes interconnected on a substrate with printed wires and printed passive components; the S/360 M85 and M91 did use ICs for some of their circuits. IBM's 1971 System/370 used ICs for their logic, and later models used semiconductor memory.

By 1971, the ILLIAC IV supercomputer was the fastest computer in the world, using about a quarter-million small-scale ECL logic gate integrated circuits to make up sixty-four parallel data processors.D. A. Slotnick, The Fastest Computer, Scientific American February 1971, reprinted in Computers and Computation, Freeman and Company, San Francisco, California, 1971,