1. Review for Quiz-1 Applied Operating System Concepts Patterson & Hennessy Chap.s 1,2,6,7 ECE3055b, Spring 2005 http://www.csc.gatech.edu/copeland/jac/3055/ppt/Review%20for%20Quiz-1.ppt

2. What is an Operating System? A program that acts as an intermediary between a user of a computer and the computer hardware. Operating system goals: –Execute user programs and make solving user problems easier. –Make the computer system convenient to use. Use the computer hardware in an efficient manner. Make it easy to write programs by handling common tasks like text editing and file-selection dialog boxes. 2

3. What characterizes the following OS types? Simple Batch Systems Multiprogramming Batched Systems Time-Sharing Systems Personal-Computer Systems Parallel Systems Distributed Systems Real -Time Systems Clustered Systems 3

4. 1.Hardware – provides basic computing resources (CPU, memory, I/O devices). 2.Operating system – controls and coordinates the use of the hardware among the various application programs for the various users. 3.Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs). 4.Users (people, machines, other computers). Computer System Components 4

5. OS Features Needed for Multiprogramming I/O routine supplied by the system. Memory management – the system must allocate the memory to several jobs. CPU scheduling – the system must choose among several jobs ready to run. Allocation of devices. Types: Batch, Parallel, Real Time, Interactive (special features) 5

6. Traditional computing –PCs, Servers, limited remote access Web-Based Computing –Client-server and web services, convenient remote access, location-less servers Embedded Computing –Most computers (auto engine controllers, microwaves) –Very limited operating system features –Little or no user interface, remote access Computer System Environments 6

7. Instruction Set Architecture - Must Match CPU Architecture C code: X = Y + Z ; Assembly (for MIPS):lw $8, Y lw $9, Z add $10, $8, $9 sw $10, X Machine Language (for MIPS, “add $10, $8, $9”): 000000 01000 01001 01010 00000 100000 opcode reg-a reg-b reg-w alu-function In decimal: op=0, rs=8, rt=9, rd=10, shamt=0, addr/funct=32 MIPS is a RISC. All machine instructions are 32-bits long. (Name a CISC computer architecture) 7

8. Branches (relative, conditional*) Jumps (absolute address, non-conditional*) Subroutine calls (return to instruction after call) * feature of MIPS architecture (How are arrays positioned in memory?) The Power of Computing comes from Decisions (if’s) and Iteration (loops and arrays) 8

9. Memory Addressing Modes Register (32-bit absolute). Offset ( 16-bit offset, sign extend, add to 32-bit base from register). Instruction Addressing ( 16-bit offset, sign extend, multiply by 4 ("<<2") add to 32-bit base from PC register). 9

10. 10 Finite-State Machine - PLA (programmable logic array) Op5 Op4 Op3 Op2 Op1 Op0 State3 State2 State1 State0 PCWrite PCWriteCond IorD MemRead MemWrite IRWrite MemtoReg PCSource1 PCSource0 ALUop1 ALUop0 ALUsrce1 ALUsrce0 ALUsrce RegWrite RegDst NextState3 NextState2 NextState1 NextState0 Orange dots are AND gates "1" Output

11. Pipelining Improve performance by increasing instruction throughput Cycles can be different time durations. Cycle always the longest time duration. Ideal speedup is number of stages in the pipeline. Do we achieve this? What reduces the speedup that is possible? 11

12. Hazards –structural hazards: suppose we had only one memory –control hazards: need to worry about branch instructions –data hazards: an instruction depends on a previous instruction (a "Dependency) What is a "Stall", when is it needed? What is a "Flush", when is it needed? (Branching, Exceptions, Subroutine call) Software Solution: Where do we insert the “nops” ? sub$2, $1, $3 and $12, $2, $5 or$13, $6, $2 add$14, $2, $2 sw$15, 100($2) What is "Dynamic Scheduling", "Superscalar Architecture"? Pipelining Problems 12

13. Memory Hierarchy What are the three main levels of memory hierarchy found in modern PC's? What is "temporal locality", "spatial locality"? How do they help us? How do the following work: Direct mapped cache Wide-memory (cache) organization What does the "Valid bit", "Index", and "Tag" do when looking for data in the cache? 13