计算机组成原理 Principles of Computer Composition

Overview

This course is really hard-core and difficult. We mainly learned about:

• von Neumann Computer Architecture

• Arithmetic Unit: Single-Bus, Dual-Bus, Triple-Bus

• Memory Hierarchy

• CPU

一、von Neumann Computer Architecture

Modern computers are designed according to the von Neumann architecture.

See in Introduction to Computer.

二、Arithmetic Unit

The main function of computer is computation. And that's what the arithmetic unit is for.

Arithmetic Unit consists of ALU(Arithmetic Logic Unit), registers, buffers, etc.

There are three types of organizations for the unit:

1) Single-Bus Organization

Only one operand can be on the bus at the same time.

The calculation speed is slow, but the control circuit is simple.

2) Double-Bus Organization

Two operands can enter the ALU at the same time.

3) Triple-Bus Organization

Two inpu of the ALU are respectively connected to a bus, and the output of the ALU is connected to the third bus.

三、Memory Hierarchy

1. Hierarchy

The memory hierarchy of modern computers has 4 layers:

• External Storage Devide: Harddisk
• Main Memory: Store Running Processes
• Cache
• Registers in CPU

2. Cache

We use cache to solve the problem of speed mismatch between CPU and Main Memory.

The computing speed of the CPU is too fast, and the main memory cannot keep up with it.

To solve this problem, we can place a high-speed memory between them to store buffered data in advance.

The process of CPU reading a word from main memory:

st=>start: start reading
op1=>operation: transfer word from cache to CPU
op2=>operation: transfer word from main memory to CPU
op3=>operation: sends entire data block containing word to cache
cond=>condition: is in cache
e=>end: finished

st->cond
cond(yes)->op1->e
cond(no)->op2->op3->e

四、CPU

CPU is the core component of the computer.

It consists of composed of arithmetic unit and controller

1. Datapath of CPU Model

2. Controller

We learned about the microprogram controller.

We split a machine instruction into several micro instructions.

Each micro instruction contains multiple micro-operations, such as flipping the enable signal of ALU.

The task of the microprogram controller is to read different microinstructions according to the machine instructions and perform corresponding operations.

五、Curriculum Design

We were asked to use Proteus to implement a simple CPU.
We need to design the clock signal generator, microprogram controller, arithmetic unit, etc.

This simple CPU can implement 8 kinds of instructions, such as arithmetic operations and storage, access, conditional transfer, etc.

Datapath of the CPU: