Chp2:Computer System Structures

1. Asynchronous I/O

1.1. can support multiple I/O setting

1.2. CPU must be fully utilize

1.3. OS indexes into I/O device table to determine device status and modify table entry to include interrupt

2. Storage Structure

2.1. Main memory

2.1.1. large storage media that CPU can access

2.2. Secondary Storage

2.2.1. extansion of main memory that provides nonvolatile storage capacity

3. Storage Hierarchy

3.1. storage system

3.1.1. speed

3.1.2. cost

3.1.3. volatility

4. Modes of operation

4.1. User mode

4.1.1. user program executes here

4.2. Kernel mode

4.2.1. monitor executes here

5. Protection

5.1. I/O

5.1.1. user program cannot issue I/O instructions directly

5.2. Memory

5.2.1. Base register

5.2.2. Limit register

5.3. CPU

5.3.1. When timer interrupt,control transfers to OS

5.3.2. Load-timer is a privileged instruction

6. Interupt Handling

6.1. When CPU is interrupted,it stops what it's doing and transfers execution to fixed location.

7. Synchronous I/O Structure

7.1. only support one I/O at a time

7.2. wait instruction idles the CPU untill next interupt

7.3. one I/O request is outstanding at a time.