History of computing hardware (1960s–present)

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 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, GE 635. 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. In the descriptions below, NSI is the next sequential instruction, the return address. Some examples are:
; Automatically record the 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 and RCA 501
; 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
; 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 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.

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 Mohamed M. Atalla at Bell Labs in the late 1950s.

Computers using IC chips began to appear in the early 1960s. For example, the 1961 Semiconductor Network Computer (Molecular Electronic Computer, Mol-E-Com), 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, 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.

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.

Third-generation computers were offered well into the 1990s; for example the IBM ES9000 9X2 announced April 1994 used 5,960 ECL chips to make a 10-way processor. Other third-generation computers offered in the 1990s included the DEC VAX 9000 (1989), built from ECL gate arrays and custom chips, and the Cray T90 (1995).

Fourth generation

Third-generation minicomputers were essentially scaled-down versions of mainframe computers, whereas the fourth generation's origins are fundamentally different. The basis of the fourth generation is the microprocessor, a computer processor contained on a single large-scale integration (LSI) MOS integrated circuit chip.

Microprocessor-based computers were originally very limited in their computational ability and speed and were in no way an attempt to downsize the minicomputer. They were addressing an entirely different market.

Processing power and storage capacities have grown beyond all recognition since the 1970s, but the underlying technology has remained basically the same of large-scale integration (LSI) or very-large-scale integration (VLSI) microchips, so it is widely regarded that most of today's computers still belong to the fourth generation.

Semiconductor memory

The MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959. In addition to data processing, the MOSFET enabled the practical use of MOS transistors as memory cell storage elements, a function previously served by magnetic cores. Semiconductor memory, also known as MOS memory, was cheaper and consumed less power than magnetic-core memory. MOS random-access memory (RAM), in the form of static RAM (SRAM), was developed by John Schmidt at Fairchild Semiconductor in 1964. In 1966, Robert Dennard at the IBM Thomas J. Watson Research Center developed MOS dynamic RAM (DRAM). In 1967, Dawon Kahng and Simon Sze at Bell Labs developed the floating-gate MOSFET, the basis for MOS non-volatile memory such as EPROM, EEPROM and flash memory.

Microprocessors

The microprocessor has origins in the MOS integrated circuit (MOS IC) chip. The MOS IC was fabricated by Fred Heiman and Steven Hofstein at RCA in 1962. Due to rapid MOSFET scaling, MOS IC chips rapidly increased in complexity at a rate predicted by Moore's law, leading to large-scale integration (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on a single MOS LSI chip.

The earliest multi-chip microprocessors were the Four-Phase Systems AL1 in 1969 and Garrett AiResearch MP944 in 1970, each using several MOS LSI chips. On November 15, 1971, Intel released the world's first single-chip microprocessor, the 4004, on a single MOS LSI chip. Its development was led by Federico Faggin, using silicon-gate MOS technology, along with Ted Hoff, Stanley Mazor and Masatoshi Shima. It was developed for a Japanese calculator company called Busicom as an alternative to hardwired circuitry, but computers were developed around it, with much of their processing abilities provided by one small microprocessor chip. The dynamic RAM (DRAM) chip was based on the MOS DRAM memory cell developed by Robert Dennard of IBM, offering kilobits of memory on one chip. Intel coupled the RAM chip with the microprocessor, allowing fourth generation computers to be smaller and faster than prior computers. The 4004 was only capable of 60,000 instructions per second, but its successors brought ever-growing speed and power to computers, including the Intel 8008, 8080 (used in many computers using the CP/M operating system), and the 8086/8088 family. (The IBM personal computer (PC) and compatibles use processors that are still backward-compatible with the 8086.) Other producers also made microprocessors which were widely used in microcomputers.

The following table shows a timeline of significant microprocessor development.

Supercomputers

The powerful supercomputers of the era were at the other end of the computing spectrum from the microcomputers, and they also used integrated circuit technology. In 1976, the Cray-1 was developed by Seymour Cray

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