( 2) Memory applications Memory can be categorized by application. Several types of memory are summarized below.
Type |
Characteristics |
Main memory |
Memory that stores programs and data that the CPU processes. |
DRAM is used for this purpose. |
Cache memory
VRAM
Memory used to speed up computers by absorbing the difference in the access speeds of the CPU and main memory. Many computers are equipped with multiple cache memory, which are called“ primary cache memory” and“ secondary cache memory” based on their proximity to the CPU. SRAM is used for this purpose.
Dedicated memory for temporary storage of image data shown on the display. VRAM is typically provided separately from the main memory, and is integrated into graphics accelerator boards. DRAM is used for this purpose.
Due to the difference in the processing speed of the CPU( fast) and main memory( slow),“ cache memory” is used to fill in the gap between processing speeds. High-speed cache memory is used to store previously accessed data. Instead of accessing the slow main memory each time, the same data is next accessed by reading it from the cache memory. Faster throughput is achieved by reducing the frequency of accessing the main memory.
Chapter 8 Computer system
When cache memory is not available
Without cache memory, data is constantly exchanged between the CPU and main memory, which incurs a wait time for the CPU and lowers processing efficiency.
Slow
CPU
Main memory DRAM
When cache memory is available
Fast Slow
CPU
Primary cache memory
SRAM
Secondary cache memory
Main memory DRAM
Fast speed, small volume
Slow speed, large volume
Data is stored in the cache memory when the CPU reads it from the main memory. The next time the same data is used, the CPU reads the data from the cache memory, which improves processing efficiency.
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