CS250 VLSI Systems Design Fall 2011 Krste Asanovic John Wawrzynek with John Lazzaro and Brian Zimmer TA Lecture 01 Introduction 1 CS250 UC Berkeley Fall 11 Why the heck is it CS250 and not EE250 We answer that with a course history with a few embedded lessons Warning What follows is principally from memory I ve done my best to be accurate but some errors or misinterpretations might exist Starts in 1958 with the invention of the Integrated Circuit independently by Robert Noyce co founder of Fairchild Semiconductor Corporation and Jack Kilby engineer at Texas Instruments Lecture 01 Introduction 1 2 CS250 UC Berkeley Fall 11 IC Design in the 70 s and early 80 s Circuit design layout and processing tightly linked Logic design and layout was random Chip design was the domain of industry Fairchild Intel Texas Instruments These were IC processing companies Those who controlled the physics controlled the creative agenda Federico Faggin Ted Hoff Stan Mazor Introduced to help sell memory chips The Intel 4004 microprocessor which was introduced in 1971 The 4004 contained 2300 transistors and performed 60 000 calculations per second Courtesy Intel Lecture 01 Intro 3 CS250 UC Berkeley Fall 11 Meanwhile at Caltech Car ver Mead was designing and building prototype ICs with help from his friends at Intel His background was in physical electronics invented several semiconductor devices such as the GaAs MESFET but was deeply interested in the interaction of physical implementation and the higher level design of electronic systems Listen to the silicon find out what it s telling you Lecture 01 Introduction 1 4 CS250 UC Berkeley Fall 11 CS At Caltech Ivan Sutherland became founding head of the computer science division at CIT in 1974 after leaving E S He and Mead teamed up to get the division off the ground making IC design Integrated Systems a key component of the research and teaching My take These t wo believed that IC design was at the heart of computer science because CS was largely about inventing and building computing devices The future of computing was integrated circuits Very flexible boundless growth potential was on an exponential grow cur ve with no end in sight Close to pure thought with few constraints and nasty realities The potential of LSI was not going to be reached with the status quo in industry Worked together over the next 6 years to establish the faculty industrial ties curriculum research projects with silicon structures as a key component They set off to build their own machines OM1 OM2 Lecture 01 Introduction 1 5 CS250 UC Berkeley Fall 11 Pushing for ward 1 The reality of integrated circuits Wires are expensive area delay power transistors are cheap Pre ICs the opposite was true Therefore plan the communication and the layout Exploit locality think about the geometry of the problem from the beginning Choose algorithms designs accordingly Algorithms designs represented as communication graphs in a large number of dimensions not a good idea Lecture 01 Introduction 1 6 CS250 UC Berkeley Fall 11 Pushing For ward 2 Put IC design expertise into the hands of those best qualified to take advantage of its potential Those with intimate knowledge of computation and algorithms computer scientists Traditionally IC design had been stratified Algorithm architecture Microarchitecture Circuit design Layout Emergence of the tall thin designer Spans all levels of the design and implementation stack Would lead to more successful innovation and highly optimized designs Lecture 01 Introduction 1 CS250 UC Berkeley Fall 11 7 Pushing For ward 3 How to enable system architects Managing the complexity was the key challenge Manipulating multiple levels of design complexity was difficult and projected to get much worse looking for ward remember Moore s Law Providing universal access to IC fabrication Solutions 1 Ideas from soft ware 2 New design representations 3 Computer aided design tools All linked 4 Silicon foundries 5 Education Lecture 01 Introduction 1 8 CS250 UC Berkeley Fall 11 Ideas from Programming help manage complexity Structured Programming was getting popular Dijstra el al No goto statements Block organization Use of hierarchy abstraction sub routines Structured Design for ICs Exploit regularity and symmetry Use and reuse common sub blocks flip flops gates arithmetic etc Represent designs hierarchically Lecture 01 Introduction 1 9 CS250 UC Berkeley Fall 11 Design Representations 1 Previously to generate the mask information for fabrication the designed needed intimate knowledge of the manufacturing process Even once this knowledge was distilled to a set of Geometric Design Rules this set of rules was voluminous with many special cases Mead and associates come up with a much simplified set of design rules single page description A sort of API or abstraction of the process back end processing could automatically convert this information into masks Sufficiently small set that designers could memorize Sufficiently abstract to allow process engineers to shrink the process and preserve existing layouts Process resolution becomes a parameter Lecture 01 Introduction 1 10 CS250 UC Berkeley Fall 11 Scalable CMOS Design Rules Created with the transition from nMOS to CMOS a much nicer technology around 1985 Little changed over the years Lecture 01 Introduction 1 CS250 UC Berkeley Fall 11 11 Design Representations 2 Caltech Intermediate Form CIF Capture layout information needed to generate masks and process ASCII text file with geometric primitives and hierarchical definitions A sample CIF wire statement The statement is W25 100 200 100 100 200 200 300 200 Simple and human readable Easy to generate and parse Common sub blocks could be reused from one design to the next output pad drivers etc Lecture 01 Introduction 1 12 CS250 UC Berkeley Fall 11 Design Representations 3 Previously designed were represented by hand drawings Then masks where made by transferring drawings to rubylith Base layer of heavy transparent dimensionally stable Mylar A thin film of deep red cellophane like material covers the base layer Patterns formed by cutting often by hand the transparent covering Using an electronic format CIF meant Layouts easily stored and transmitted Written to tape and transferred to manufacturer tape out Transmitted over the net work new idea back then Soft ware could automatically check for layout errors Generated from a program huge idea Lecture 01 Introduction 1 13 CS250 UC Berkeley Fall 11