CS61C Machine Structures Lecture 20 Introduction to Synchronous Digital Systems 3 6 2006 John Wawrzynek www cs berkeley edu johnw www inst eecs berkeley edu cs61c CS 61C L20 Synchronous Digital Systems 1 Wawrzynek Spring 2006 UCB Below the Program High level language program in C swap int v int k int temp temp v k v k v k 1 v k 1 temp C compiler Assembly language program for MIPS swap sll add lw lw sw sw jr 2 5 2 2 4 2 15 0 2 16 4 2 16 0 2 15 4 2 31 assembler Machine object code for MIPS 000000 00000 00101 0001000010000000 000000 00100 00010 0001000000100000 CS 61C L20 Synchronous Digital Systems 2 Wawrzynek Spring 2006 UCB What are Machine Structures Application Netscape Compiler Software Hardware Assembler 61C Operating System MacOS X Processor Memory I O system Instruction Set Architecture Datapath Control Digital Design Circuit Design transistors Coordination of many levels of abstraction ISA is an important abstraction level contract between HW SW CS 61C L20 Synchronous Digital Systems 3 Wawrzynek Spring 2006 UCB Synchronous Digital Systems The hardware of a processor such as the MIPS is an example of a Synchronous Digital System Synchronous Means all operations are coordinated by a central clock It keeps the beat of the system Digital Mean all values are represented by discrete values Electrical signals are treated as 1 s and 0 s and grouped together to form words CS 61C L20 Synchronous Digital Systems 4 Wawrzynek Spring 2006 UCB Logic Design Next 4 weeks we ll study how a modern processor is built starting with basic elements as building blocks Why study hardware design Understand capabilities and limitations of hardware in general and processors in particular What processors can do fast and what they can t do fast avoid slow things if you want your code to run fast Background for more detailed hardware courses CS 150 CS 152 There is just so much you can do with processors At some point you may need to design your own custom hardware CS 61C L20 Synchronous Digital Systems 5 Wawrzynek Spring 2006 UCB PowerPC Die Photograph Let s look closer CS 61C L20 Synchronous Digital Systems 6 Wawrzynek Spring 2006 UCB Transistor Circuit Rep vs Block diagram Chips is composed of nothing but transistors and wires Small groups of transistors form useful building blocks Block are organized in a hierarchy to build higher level blocks ex adders CS 61C L20 Synchronous Digital Systems 7 Wawrzynek Spring 2006 UCB The Clock Signal CS 61C L20 Synchronous Digital Systems 8 Wawrzynek Spring 2006 UCB Signals and Waveforms CS 61C L20 Synchronous Digital Systems 9 Wawrzynek Spring 2006 UCB Signals and Waveforms Grouping CS 61C L20 Synchronous Digital Systems 10 Wawrzynek Spring 2006 UCB Signals and Waveforms Circuit Delay CS 61C L20 Synchronous Digital Systems 11 Wawrzynek Spring 2006 UCB Type of Circuits Synchronous Digital Systems are made up of two basic types of circuits Combinational Logic CL circuits Our previous adder circuit is an example Output is a function of the inputs only Similar to a pure function in mathematics y f x No way to store information from one invocation to the next No side effects State Elements circuits that store information CS 61C L20 Synchronous Digital Systems 12 Wawrzynek Spring 2006 UCB Circuits with STATE e g register CS 61C L20 Synchronous Digital Systems 13 Wawrzynek Spring 2006 UCB And in conclusion ISA is very important abstraction layer Contract between HW and SW Clocks control pulse of our circuits Voltages are analog quantized to 0 1 Circuit delays are fact of life Two types of circuits Stateless Combinational Logic State circuits e g registers CS 61C L20 Synchronous Digital Systems 14 Wawrzynek Spring 2006 UCB
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