@[TOC]

Modern computer architecture

The hierarchical structure of memory

Each hierarchy of memory:Note: Data in auxiliary memory cannot be accessed by CPU until it is called into main memory

* Cache pronunciation is as follows:Fanyi.baidu.com/?aldtype=85…

Problems resolved between relationships

  • Primary/secondary storage: Implements the virtual storage system to solve the problem of insufficient main storage capacity
  • Cache-main memory: Resolves the mismatch between main memory and CPU speed

Price comparison of each layer of memory speed capacity

Note: some textbooks call the disk installed inside the computer “auxiliary storage”, and U disk, CD, etc., “external storage”. Some textbooks refer to disk, U disk, CD as “auxiliary storage” or “external storage”

Classification of memory

level

The storage is divided into layers

medium

Classified by storage media

1. Semiconductor memory (with semiconductor devices to store information) (main memory, Cache)

2. Magnetic surface memory: disk, tape (magnetic material to store information)

3. Optical memory (storing information in magnetic materials)

Access mode

  1. An Associative Memory is a ContentAddressed Memory (CAM) that can be used for reading and writing by retrieving the contents to a storage location

  2. RandomAccess Memory (RAM) : it takes the same time to read and write any Memory location, regardless of its physical location

  3. SequentialAccess Memory (SAM) : the time required to read and write a storage unit depends on its physical location

  4. DirectAccessMemory (DAM) has both random access and sequential access. Directly select the area where the information is located, and then access it in sequence.

  5. Serial access memory: The time required to read and write a storage unit depends on the physical location of the storage unit

Information can be modified

  1. Read/Write Memory – both readable and writable (e.g., disk, Memory, Cache)
  2. Physical music albums are usually cD-ROMs, movies are blu-ray, and BIOS is usually written in ROM. In fact, many ROMs can be Read and written multiple times, but it is more troublesome. = =

The conservability of information

  1. Memory in which information is lost after a power failure — == Volatile memory == (main memory, Cache)

  2. Memory that retains information after a power failure — == Nonvolatile memory == (disk, CD)

  • Destruction of the original stored information after a readout – destructive readout (as on DRAM chips, the data is rewritten after being read)
  • After the information is read, the original stored information is not destroyed – non-destructive read (e.g. SRAM chip, disk, CD)

Performance indicators of memory

  1. Storage capacity: storage space x word length (for example, 1M x 8 bits). == (MDR bit mirroring memory word length) ==
  2. Unit cost: Price per person = total cost/total capacity.
  3. Storage speed: Data transfer rate = data width/storage period. ==, == (Main memory bandwidth (Bm) == : Main memory bandwidth is also called == Data transfer rate ==, indicating the maximum amount of information sent in and out of main memory per second. The unit is word/second, byte/second (B/s), or bit/second (B/s).

Storage time, storage period:

① == Access time (Ta) == : Access time refers to the time from the start of a memory operation to the completion of the operation, which is divided into read time and write time. ②== Access cycle (Tm) == : Access cycle is also called read/write cycle or access cycle. It refers to the total time required for a complete read and write operation to the memory, that is, the minimum time required between two consecutive independent access memory operations (read or write operations).

The following figure shows the relationship between storage time and storage period:

summary