What is VLSI?
VLSI stands for "Very Large Scale Integration". This is the field which involves packing more and more logic devices into smaller and smaller areas.Thanks to VLSI, circuits that would have taken boardfuls of space can now be put into a small space few millimeters across!
Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistors into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device
This has opened up a big opportunity to do things that were not possible before. VLSI circuits are everywhere ... your computer, your car, your brand new state-of-the-art digital camera, the cell-phones, and what have you. VLSI has been around for a long time, there is nothing new about it ... but as a side effect of advances in the world of computers, there has been a dramatic proliferation of tools that can be used to design VLSI circuits.
Alongside, obeying Moore's law, the capability of an IC has increased exponentially over the years, in terms of computation power, utilisation of available area, yield. The combined effect of these two advances is that people can now put diverse functionality into the IC's, opening up new frontiers
The first semiconductor chips held two transistors each. Subsequent advances added more and more transistors, and, as a consequence, more individual functions or systems were integrated over time. The first integrated circuits held only a few devices, perhaps as many as ten diodes, transistors, resistors and capacitors, making it possible to fabricate one or more logic gates on a single device. Now known retrospectively as small-scale integration (SSI), improvements in technique led to devices with hundreds of logic gates, known as medium-scale integration (MSI). Further improvements led to large-scale integration (LSI), i.e. systems with at least a thousand logic gates. Current technology has moved far past this mark and today's microprocessors have many millions of gates and billions of individual transistors.
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 greater than VLSI levels of integration are no longer in widespread use.
As of early 2008, billion-transistor processors are commercially available. This is expected to become more commonplace as semiconductor fabrication moves from the current generation of 65 nm processes to the next 45 nm generations (while experiencing new challenges such as increased variation across process corners). A notable example is Nvidia's 280 series GPU. This GPU is unique in the fact that almost all of its 1.4 billion transistors are used for logic, in contrast to the Itanium, whose large transistor count is largely due to its 24 MB L3 cache. Current designs, as opposed to the earliest devices, use extensive design automation and automated logic synthesis to lay out the transistors, enabling higher levels of complexity in the resulting logic functionality. Certain high-performance logic blocks like the SRAM (Static Random Access Memory) cell, however, are still designed by hand to ensure the highest efficiency
