Computer Aided Design

Tools for developing Chips

The semiconductor business had changed significantly since the early 1960s and 1970s. As described, the number of transistors on a chip doubled every two years. This inevitably led to the fact that the layout of chips could no longer be handled “manually” for certain applications. New technologies were needed to support the complex designs. These were called Electronic Design Automation (EDA) and Computer-Aided Design (CAD).

MEAD-CONVAY REVOLUTION IN VLSI DESIGN

Two scientists, Lynn Conway and Carver Mead, developed special design rules for chip design at Xerox PARC in the 1970s. Her book, Introduction to VLSI (Very Large Scale Integration) Systems, became the “bible” of chip developers and sparked a revolution in chip design. Above all, it was the basis for Electronic Design Automation. In 1979, a student of Carver Mead provided the first description of a silicon compiler that enabled chip design automatically from a “design description” of the chip. Such compilers were realized in the beginning of the eighties.

VHDL

In 1980, the American government realized, that the American semiconductors industry was in danger of losing its leading position. It launched a program to promote IC design called Very High Speed Integrated Circuit (VHSIC). The goal was to develop a language that could be used to describe a digital chip. This language was called VHSIC Description Language for short VHDL. The Ministry of Defense even required that all chips developed e.g. for US Military must be described in VHDL. A first version of the VHDL compiler was created in 1985. Since then, VHDL is standardized by IEEE.

Design Flow using VHDL language

VHDL is somewhat similar to normal SW high-level languages. It is possible to define and simulate systems without having to immediately simulate a “physical realization”. The focus of VHDL is description and verification. The result of a compilation is a netlist which consist on a network of logical gate. This netlist can be used for simulation. It can also be optimized (towards less gates). Finally a netlist can be used for a „place and route SW“. This place and route creates physical gates and physical connections.

VLSI Technologies

The semiconductor company VLSI Technologies, founded in 1979, became a pioneer in EDA SW. VLSI Technologies originally wanted to produce chips for external companies. However, VLSI’s investors pushed for VLSI to develop software that made chip design easier for outside companies. VLSI created design tools including silicon compilers for creating ASICs. However, at the end of the 1980s, VLSI lost the advantages of these design tools as they were increasingly created by external EDA companies, which also made them available to other semiconductor companies. Nevertheless, VLSI remained a leading producer of ASICs.

EDA Companies

In the 1980s, new companies emerged in Silicon Valley that specialized in software for the simulation and synthesis of chips. Many of these developments came from the Mead-Convey community and from specialist in VLSI design.

  • Mentor Graphics founded in 1981
  • Synopsis founded in 1986
  • Cadence founded in 1988