Very-large-scale integrationVery-large-scale integration (VLSI) of systems of transistor-based circuits into integrated circuits on a single chip first occurred in the 1980s as part of the semiconductor and communication technologies that were being developed. The first semiconductor chips held one transistor each. Subsequent advances added more and more transistors, and as a consequence more individual functions or systems were integrated over time. The microprocessor is a VLSI device. The first "generation" of computers relied on vacuum tubes. Then came discrete semiconductor devices, followed by integrated circuits. The first Small-Scale Integration (SSI) ICs had small numbers of device on a single chip - diodes, transistors, resistors and capacitors (no inductors though), making it possible to fabricate one or more logic gates on a single device. The fourth generation consisted of Large-Scale Integration (LSI), i.e. systems with at least a thousand logic gates. The natural successor to LSI was VLSI (many tens of thousands of gates on a single chip). Current technology has moved far past this mark and today's microprocessors have many million gates and hundreds of millions of individual transistors. As of mid-2004, billion-transistor processors are not yet economically feasible for most uses, but they are achievable in laboratory settings, and they are clearly on the horizon as semiconductor fabrication moves from the current generation of 90 nanometer (90nm) processes to the next 65nm and 45nm generations. At one time, there was an effort to name and calibrate various levels of large-scale integration above VLSI. Terms like Ultra-large-scale Integration (ULSI) were used. But the huge number of gates and transistors available on common devices has rendered such fine distinctions moot. Terms suggesting more-than-VLSI levels of integration are no longer in widespread use. Even VLSI is now somewhat quaint, given the common assumption that all microprocessors are VLSI or better. Further reading
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