Synthesis is a crucial component of future CAll s;ystems. The competitive edge of IC desiBn will most probcbly come frc*'1l the use of effective synthesis tools. A complete synthesis system should generate layout masks from a high-level algorithmic, behavioral or functional des- cription of a VLSI systen, [1 description of the target tech- nology and a description of the constraints and cost func- tions. The design should be completed in reasonable time and with the quality a human designer could obtain. Working designs have been produced with silicon compilers, but the quality of the design has always been a problem. ~n1ile for a restricted class of designs, such 2S Digital Signal Processors (DSP) , the use of a fixed floor-plan has been successful, its use for less constrp.ined applications results in inefficient utilizstion of areE and poor perfor- mance. In addition, the structure of the control logic is of- ten too rigid end not optimized, thus yielding F: slm'! and large chip. The present trend is to bre8t: the synthesis pro- cess into stages, end to use tools thet optimize rep.l estate Bnd/or performance to go from one stege to the next. This book covers most of the topics in the design of di- gital VLSI Circuits, 2nd focuses on theory, as well as algo- rithms and co~puter implementations of desiGn systems.

The Nato Advanced Study Institute on "Computer Design Aids for VLSI Circuits" was held from July 21 to August 1, 1980 at Sogesta, Urbino, Italy. Sixty-three carefully chosen profes sionals were invited to participate in this institute together with 12 lecturers and 7 assistants. The 63 participants were selected from a group of almost 140 applicants. Each had the background to learn effectively the set of computer IC design aids which were presented. Each also had individual expertise in at least one of the topics of the Institute. The Institute was designed to provide hands-on type of experience rather than consisting of solely lecture and discussion. Each morning, detailed presentations were made concerning the critical algorithms that are used in the various types of computer IC design aids. Each afternoon a lengthy period was used to provide the participants with direct access to the computer programs. In addition to using the programs, the individual could, if his expertise was sufficient, make modifications of and extensions to the programs, or establish limitations of these present aids. The interest in this hands-on activity was very high and many participants worked with the programs every free hour. The editors would like to thank the Direction of SOGESTA for the excellent facilities, 1r. R. Riccioni of the SOGESTA Computer Center and Mr. 11. Vanzi of the University of Genova for enabling all the programs to run smoothly on the set date. P.Antognetti D.O.Pederson Urbino, Summer 1980."

P. Antognetti University of Genova, Italy Director of the NATO ASI The key importance of VLSI circuits is shown by the national efforts in this field taking place in several countries at differ ent levels (government agencies, private industries, defense de partments). As a result of the evolution of IC technology over the past two decades, component complexi ty has increased from one single to over 400,000 transistor functions per chip. Low cost of such single chip systems is only possible by reducing design cost per function and avoiding cost penalties for design errors. Therefore, computer simulation tools, at all levels of the design process, have become an absolute necessity and a cornerstone in the VLSI era, particularly as experimental investigations are very time-consuming, often too expensive and sometimes not at all feasible. As minimum device dimensions shrink, the need to understand the fabrication process in a quanti tati ve way becomes critical. Fine patterns, thin oxide layers, polycristalline silicon interco~ nections, shallow junctions and threshold implants, each become more sensitive to process variations. Each of these technologies changes toward finer structures requires increased understanding of the process physics. In addition, the tighter requirements for process control make it imperative that sensitivities be unde~ stood and that optimation be used to minimize the effect of sta tistical fluctuations.

We are about to enter a period of radical change in computer architecture. It is made necessary by adL)anCeS in processing tech- nology that will make it possible to build devices exceeding in performance and complexity anything conceived in the past. These advances the logical extension of large - to very-large-scale in- J tegration (VLSI) are all but inevitable. With the large number of shlitching elements available in a sinqle chip as promised by VLSI technology, the question that arises naturally is: What can hle do hlith this technology and hOhl can hle best utilize it? The final anShler, hlhatever it may be, hlill be based on architectu- ral concepts that probably hlill depart, in several cases, from past and present practices. Furthermore, as hle continue to build increasingly pOhlerful microprocessors permitted by VLSI process advances, the method of efficiently interconnecting them hlill become more and more important. In fact one serious drahlback of VLSI technology is the limited number of pins on each chip. While VLSI chips provide an exponentially grOhling number of gates, the number of pins they provide remains almost constant. As a result communication becomes a very difficult design problem in the interconnection of VLSI chips. Due to the insufficient commu- nication pOhler and the high design cost of VLSI chips, computer systems employing VLSI technology hlill thus need to employ many architectural concepts that depart sharply from past and present practices.

Synthesis is a crucial component of future CAll s;ystems. The competitive edge of IC desiBn will most probcbly come frc*'1l the use of effective synthesis tools. A complete synthesis system should generate layout masks from a high-level algorithmic, behavioral or functional des- cription of a VLSI systen, [1 description of the target tech- nology and a description of the constraints and cost func- tions. The design should be completed in reasonable time and with the quality a human designer could obtain. Working designs have been produced with silicon compilers, but the quality of the design has always been a problem. ~n1ile for a restricted class of designs, such 2S Digital Signal Processors (DSP) , the use of a fixed floor-plan has been successful, its use for less constrp.ined applications results in inefficient utilizstion of areE and poor perfor- mance. In addition, the structure of the control logic is of- ten too rigid end not optimized, thus yielding F: slm'! and large chip. The present trend is to bre8t: the synthesis pro- cess into stages, end to use tools thet optimize rep.l estate Bnd/or performance to go from one stege to the next. This book covers most of the topics in the design of di- gital VLSI Circuits, 2nd focuses on theory, as well as algo- rithms and co~puter implementations of desiGn systems.