The third generation of computers began with IBM's announcement of System/360 in 1964. IBM worked to reduce the size of System/360 machines by using hybrid integrated circuits, in which transistors and other components were soldered to thick-film circuits laid out on ceramic substrates. In addition, microprogramming was used extensively to create a family of machines with a single architecture, enabling the same software to run on all sizes of machines. This led to the advent of the general-purpose computer, which covered all application fields, including business computing and scientific and engineering calculations. These general-purpose computers would become known as mainframes．
Fujitsu, Oki Electric, and NEC jointly developed the large FONTAC computer with a grant from the Ministry of International Trade and Industry and delivered it to the Japan Electronic Industry Development Association in November 1964. Hitachi developed its large, general-purpose HITAC 5020 computer for scientific and engineering calculations in September 1964 and delivered the machine to Kyoto University in 1965. Japan's computer makers announced new series of third-generation computers based on these successes and through technology transfers with U.S. computer manufacturers. For example, NEC announced the NEAC-2200 series in partnership with Honeywell and Hitachi announced its HITAC 8000 series in partnership with RCA. Fujitsu, on the other hand, did not partner with any foreign firms, but instead scaled up the technology from the FONTAC, developed with a grant from the Ministry of International Trade and Industry, and announced the FACOM 230 series. After developing the TOSBAC-3400 series, Toshiba entered a technology licensing agreement with GE and announced the TOSBAC-5600 series. Mitsubishi Electric announced the MELCOM 3100 series, which replaced a machine developed in tandem with TRW, and announced the MELCOM 7000 series through a technology pact with SDS. Oki Electric developed the small-to-mid-sized OKIMINITAC series and created a domestic version of the UNIVAC through the Oki-UNIVAC joint venture with Sperry Rand．
The larger third-generation mainframe models were developed with proprietary technologies. NEC developed the 500 model of the NEAC 2000 series, which was Japan's first all-IC mainframe, in October 1966. Hitachi also independently developed the large HITAC 8500 with microprogramming control. Fujitsu completed the FACOM 230-60, which used all TTL ICs, in 1968 and delivered the machine to Kyoto University．
Seeking to adopt a standard computer to provide data communication services, the Nippon Telegraph and Telephone Public Corporation (now NTT) launched in 1967 the Dendenkosha Information Processing System (DIPS) development project. Beginning with the initial DIPS-0 pilot system, the project started developing the large, high-performance DIPS-1 computer system in partnership with NEC, Hitachi, and Fujitsu．
1970sGeneration 3.5 started in 1970 with IBM's announcement of System/370, which ushered in the use of large-scale integrated (LSI) circuits. System/370 used ICs for memory instead of magnetic cores and supported virtual memory. System/370 was also designed with backward compatibility with System/360 software to ease migration to System/370. GE withdrew from the computer business in 1970 and Honeywell Information Systems absorbed GE's computer division. RCA also left the computer industry in 1971 after announcing generation 3.5 products. UNIVAC bought RCA's user base. Domestic manufacturers announced models with greatly improved cost efficiencies to combat System/370 models. In 1971, Hitachi unveiled the HITAC 8350/8450 and NEC the NEAC 2200/375 and 575, and in 1973, Fujitsu announced the FACOM 230-8 series．
The Japanese government had protected domestic computer manufacturers because of the large gap with the United States, but in April 1971 the government switched to a policy of liberalization that would open up the domestic computer industry by December 1975. As part of this measure, the Ministry of International Trade and Industry created a system of grants for development of new product corporate groups. Accompanying the inauguration of this system, Japan's computer makers split into three alliances : Fujitsu and Hitachi, NEC and Toshiba, and Mitsubishi Electric and Oki Electric. The groups developed the M series, the ACOS series, and the COSMO series respectively. The first announcement of the M series in November 1974 consisted of two models, the M-180 and the M-190, which was followed by the May 1975 announcement of the M-160 and the M-170. Fujitsu was in charge of the M-190 and the M-160, while Hitachi managed the M-180 and M-170. The M-190, which was completed in November 1975, was the world's first all-LSI mainframe, using 100 gates/chip LSI. Fujitsu announced the M-200, the flagship of the M series, in 1978, followed by Hitachi's announcement of the M-200H．
The Next-Generation Computer Very Large-Scale Integration (VLSI) Development Assistance Grant system was established in 1975 and VLSI development grants were handed out to two groups — the Hitachi-Fujitsu-Mitsubishi group and the NEC-Toshiba group — in 1976. The grants were used to bolster the groups' hardware technology capabilities. This paved the way to the development of high-performance VLSI and the creation of powerful mainframes.
IBM announced the entry level 4331 and 4341 models as part of the IBM 4300 series in January 1979. These models represented a huge improvement in performance and cost efficiency over the previous entry-level System/370 models, in part because they used multilayer ceramic circuit boards to mount the 64 KB of IC memory and the computer's LSI logic. In February of that year, NEC announced the compact ACOS system 250, which offered competitive cost efficiency when compared to the rival IBM 4331. In April, Fujitsu announced four mid-range general-purpose computer models (the FACOM M-130F, M-140F, M-150F, and M-160F) and the JEF Japanese language information system. At the end of 1979, Mitsubishi Electric announced the COSMO 900II, the COSMO series' flagship loaded with high-speed LSI logic．
1980sIn 1980, NEC announced the top-end model of its ACOS series, the System 1000. The following year Hitachi announced the M-200 series, which outperformed its previous series, and Fujitsu announced the FACOM M-380 and the FACOM M-382, the largest general-purpose mainframes in the M-300 series. All of these mainframes had some of the highest performance levels in the world．
IBM announced the 370 extended architecture (370-XA) and the IBM 3081K in 1981, which expanded address fields from 24 bits to 31 bits, allowed virtual memory addressing up to 2 GB, and extended the actual memory space to 2 GB. Fujitsu and Hitachi adopted the same architecture. NEC expanded its ACOS-4 architecture to 31 bits in 1984.
Large mainframes in this era featured multiprocessor technology, address expansion and other extended architecture technologies, add-on modules for dedicated processes, hierarchal storage architectures for main memory, hardware-accelerated virtual machines, and beefed up RAS (reliability, availability, and serviceability) functions. The NEC ACOS System 1500, the Hitachi M-684H, and the Fujitsu M-780, all announced in 1985, could be configured with up to four CPUs and additional extended memory to give higher system performance．
The 1970s saw the emergence of IBM compatible computers in the United States, called plug-compatible machines (PCMs). Japan began exporting PCMs as well from the middle of the 1970s. In 1982, a dispute broke out with IBM over the development of IBM compatible machines．
1990sThe swift development of personal computers, LSI technology, software, and other technologies in the 1980s created a downsizing movement, which caused the mainframe market to both contract and rapidly come down in price. In 1990, the Hitachi M-880, the NEC ACOS System 3800, and the Fujitsu M-1800 were announced, with the performance of the top-end models hitting another high watermark. In addition to faster processors, these models were distinctive for extending multiple processor configurations to six to eight processors and greatly expanding main memory and extended memory capacities．
In response to the downward price pressure, low-power CMOS technology reached mainframes in 1994, as IBM announced its System/390 9672 series and NEC announced its parallel ACOS series PX7800. Fujitsu announced the large CMOS server GS8000 series in 1995. Hitachi developed a hybrid ECL-CMOS technology and started shipping its high-end MP5800 server in 1995 that carried this technology．
Internet growth exploded in the second half of the 1990s, and this, in combination with corporate globalization, spurred the transition of large general-purpose mainframe computers to core servers in global network systems, where they were used for large-scale billing and accounting and huge databases. A new need also emerged for super servers for the network computing era. As a result, the mainstream became comprehensive information processing systems that made use of the characteristics of both large general-purpose systems and open systems．
Although CMOS-based processors did not perform as well as ECL-based processors at the time, CMOS-based processors made it possible to extend multiprocessor configurations because they consumed much less power. This led to the emergence of highly efficient parallel processing architectures and a high degree of system performance scalability. CMOS processors’ performance levels quickly improved until, by the end of the 1990s, they were on par with ECL processors. From 2000 on, mainframes used CMOS processors exclusively．
NEC announced the PX7900 model in its parallel ACOS series with 32 CMOS processors in 1996 and, in 1998, announced the PX7800SV and the PX7600SV. Fujitsu announced in 1998 the GS8800, the high-end, very-large model of the GS8000 series, Fujitsu’s first to use CMOS processors. Hitachi announced in 1999 the MP6000, successor to the MP5800, using its newly developed Advanced CMOS-ECL 2 (ACE2) technology．
IBM announced a new architecture in 2000, which caused PCM manufacturers to cancel development and sales, and, thus, the PCM disappeared after a run of about a quarter of a century．