Memory - principles of computer composition

4.1 Overview

• What types of memory can be divided into?

1. Classification by storage media

• Semiconductor memory TTL MOS                                Volatile
• Magnetic surface memory                                                                                                                                                                                             not not volatile                             
• Magnetic core memory Hard magnetic material Ring element                  Not volatile
• Optical Disk Storage Laser Magneto-optical Materials                           Not Volatile

    2. Classified by access method

• Access time is independent of physical address (random access)

Random access memory can be read and written during the execution of the program

Read-only memory Read-only during program execution

• Access time is related to physical address (serial access)

sequential access memory tape

direct access memory disk

  3. Classification by function in computers

 Memory hierarchy

1. The relationship between the three main characteristics of memory

   Speed ​​Capacity Price

 Cache-main memory hierarchy and main memory-auxiliary memory hierarchy

4.2 Main memory

• Basic components of main memory

• The connection between main memory and cpu

• 

   Connected through data bus, address bus and control bus

  The data bus completes the information transmission between the CPU and the main memory, so the data bus is directly connected to the MDR and may be output or written.

  The address bus is connected between the MAR register and the address bus of the main memory. It gives the address of the unit to be accessed, so it is one-way.

• Allocation of storage unit addresses in main memory

• Main memory technical indicators

1. Storage capacity           Main memory The total number of bits stored in binary code
2. Storage speed               

 Main memory—Introduction to semiconductor chips

Basic structure of semiconductor memory chip

Chip capacity calculation: 2^10 * 4 = 1K * 4

Data cable: bidirectional

Chip select line: Chip select line, whether the selected signal is in the chip

Chip select lines are used to select memory chips

The read and write control lines determine the chip to perform read/write operations

 The number of bits in the address lines and data lines together reflects the capacity of the memory chip. For example, if there are 10 address lines and 4 data lines, the capacity of the chip is 2^10×4=4k bits; there are 14 address lines and 1 data line. Then the capacity is 16k

How to use 16k*1-bit memory chips to form 64k*8-bit memory?

 A group of eight pieces satisfies 16k*8, a total of four groups satisfies 64*8     

But every time a stored word is read out, only eight pieces need to be selected.

Decoding and driving methods of semiconductor memory chips

1. The line selection method is not suitable for chips with too large capacity. When the capacity is too large, the chip cannot integrate so many lines.

 

2. Duplication method can make the chip integration higher

 

Random access memory (RAM)

1. Static RAM (SRAM)

What is the principle of saving 0 and 1?

trigger

What is the composition of the basic unit circuit?

How to read and write to the unit circuit?

What does a typical chip structure look like?