hierarchical memory system

Memory is divided into four levels from the inside to the outside: internal registers, cache memory, internal memory, and external memory. They decrease step by step in access speed and increase step by step in storage capacity.
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internal register

The internal register is a kind of high-speed cache inside the computer processor, which is a type of high-speed memory used to store information such as temporary data and instructions. They are usually located inside the processor, and compared to other storage devices, the internal registers can be accessed faster and can be read and written within the processor clock cycle. Because the internal registers are fast, temporary, and efficient, the processor can perform various operations by continuously reading and writing internal registers.

Internal registers usually include general-purpose registers, special-purpose registers, and status registers. General-purpose registers can be used to store temporary data such as values, addresses, and pointers; special-purpose registers are used for special calculations or controls; status registers are used to store specific operating status information, such as carry flags, zero flags, overflow flags, and interrupt flags wait. The processor can access different internal registers to complete different operations according to needs, which can improve the operating efficiency and speed of the processor.

cache register

A cache register is a cache in a computer processor, also called a cache register (Cache Register). It is located inside the processor and is used to temporarily store data and instructions that the processor reads from the main memory (RAM) to speed up the execution of instructions by the processor. Because the reading and writing speed of the cache register is much faster than that of the memory, it can effectively reduce the waiting time and improve the efficiency of data reading and processing.

There are two types of cache registers: data cache and instruction cache. The data cache stores the data needed by the computer processor. For example, when performing an addition operation, two numbers need to be taken out of the memory. The calculator will store these data in the cache for access by the calculator; the instruction cache stores the data of the processor. The instruction that needs to be executed, by searching the instruction in the instruction cache, the processor can quickly obtain the instruction that needs to be executed, thereby speeding up the execution speed of the program.

Cache registers are usually larger than internal registers but smaller than main memory. Its working mode is to first copy the data and instructions in the main memory to the cache register, and then the processor directly reads and processes the data and instructions in the cache register. If you want to modify the data in the cache, you must modify the cache and main memory together to ensure data consistency.

internal memory

Internal memory, also called memory (Memory), is an important storage device in a computer, which is mainly used to store programs and data that the computer is running. The internal memory is different from external storage devices such as hard disks, CDs, and U disks. It is the main channel for data exchange between the computer processor and other hardware devices, and it is also the computer's high-speed cache.

Internal memory is generally divided into random access memory (Random Access Memory, RAM) and read-only memory (Read Only Memory, ROM). RAM improves the work efficiency of the computer by storing temporary data and program codes in the memory. It becomes a temporary memory inside the computer because of its fast read and write speed, short access time, and easy operation; Permanent fixed data and program code, once written, can only be read and cannot be modified.

The capacity of internal memory can range from tens of megabytes to tens of megabytes or even hundreds of gigabytes. Currently, common memory specifications include DDR, DDR2, DDR3, and DDR4. Memory is also one of the bottlenecks of computer performance. Choosing a memory specification suitable for your computer can improve the speed and efficiency of your computer.

Large capacity external storage

Large-capacity external storage (Large-capacity external storage) refers to a data storage device used outside the computer, which can expand the storage capacity of the computer. Large-capacity external storage includes many types, such as hard disk, solid-state hard disk, U disk, memory card (such as SD card, MicroSD card, etc.), mobile hard disk, network storage, etc.

In practical applications, many computers require large-capacity external memory to store data, especially those applications that need to process a large number of images, videos and other files. Compared with internal storage, large-capacity external storage is usually larger and cheaper, and is more suitable for large-scale data storage scenarios.

To choose a suitable large-capacity external storage, you need to consider your own needs and budget, such as storage capacity, read and write speed, transmission method, reliability, durability, and data security. When using large-capacity external storage, you should pay attention to security measures such as regular backup and multi-point storage to avoid the risk of data loss. At the same time, for more mobile external storage, attention should also be paid to the physical security of data to prevent data from being stolen or lost.