CP1300 Architecture

• Central Processing Unit (CPU)
  • Arithmetic and Logic Unit (or ALU) for arithmetic and logic operations
  • Registers - very fast pieces of memory used to store the data the ALU is using right now
    • Program Counter (PC) - address in memory of current instruction
    • Memory Address Register (MAR) - address in memory to read from or write to
    • Memory Buffer Register (MBR) - data read from or written to memory
    • Accumulator (ACC) - results of most recent operation
    • Instruction Register (IR) - the instruction currently being executed
    • Status Register (SR) - status of last instruction execution
  • Micro-memory - contains microcode for running the CPU
  • CPU is generally contained entirely on one chip

• Storage
  • Random Access Memory (RAM)
    • Holds the data and programs currently being used
    • Each location has a unique address
    • CPU can read from and write to memory, by address
    • RAM is volatile
  • Read Only Memory (ROM)
    • Contents set permanently at factory
    • Often used to hold instructions that are executed when power is turned on
    • Non-volatile
  • Cache Memory
    • Stores frequently and recently used data that is too large to leave in regeisters
    • Faster than regular memory but slower than registers
  • Secondary Storage
    • For storing large quanities of data
    • Examples
      • Disk drives (both hard drives and floppies)
      • CDROM
      • Tape drives
    • Non-volatile
    • Slower but cheaper than RAM
  • The data speed/size/cost pyramid:
    

• I/O Devices
  • Hardware for interfacing between the computer and the "real world"
  • Examples
    • Disk
    • Keyboard
    • Screen
    • Mouse
    • Printer
    • Speakers
    • Microphone
    • Sensors of various types
  • I/O devices are very slow compared to the CPU
    • Control chip interfaces with the CPU
    • CPU sends requests to the control chip
    • Control interrupts CPU when task is completed

• Communications Bus
  • Communication link between different components of the computer
    • Get an instruction from the keyboard and send it to the CPU
    • Transfer data from disk to memory
    • Transfer data from memory to the CPU
    • Transfer some data from memory to the monitor
  • A central bus connects the CPU to all other components
  • Other buses connect specific pairs of components together, e.g., a bus may connect main memory and disk drives so files can be quickly transferred
  • Usually the bus is duplex but atomic

• Transferring data between memory and the CPU
  • Reading data from memory
    • The memory address is placed in the MAR
    • A read signal is sent to memory
    • The data is transferred from memory to the MBR
    • The data is retrieved from the MBR
  • Writing data to memory
    • The memory address is placed in the MAR
    • The data is placed in the MBR
    • A write signal is sent to memory
    • The data is transferred from the MBR to memory

Self assessments

• Typical Architecture

Tutorial Questions

• Typical Architecture (Answers)

Exam style questions

1. What does a typical computer architecture consist of?
2. Describe the major components of a CPU.
3. Describe the major features of main memory.
4. What is cache memory? What is it used for? Are there other places where a cache may be used?
5. What is meant by the terms "volatile" and "non-volatile" with respect to different storage types?
6. What is the broad definition of an IO device?
7. Why do IO devices require a control chip? Give an example of a device which a control chip.
8. List some of the elements of a computer that form the communications bus.
9. State some of the features of the communications bus.
10. What are bus protocols used for?
11. Draw a diagram indicating the relationships between various kinds of memory with respect to speed, cost, and size.