Why does SSD have a read and write limit but not memory?
By Katee Cheung 2020-02-21 1663 14
However, although both use particles, SSD has a limit on the number of times it can read and write, but does not have memory. The reason for this should start from the functions of the two.
First of all, we have to understand that both SSD and memory belong to memory.
Memory, as its name implies, is a component used to store programs and data. With it, the computer has the memory function to ensure normal data reading and writing.
Memory can be divided into internal memory and external memory. The internal memory can be referred to as memory for short, and its function is to temporarily store the operational data in the CPU and exchange data with the external memory. It is characterized by fast reading and writing data, but cannot store data once the power is off.
The external memory is different, it can still save data after power off, but the disadvantage is that the reading and writing speed is slow, such as SSD, U disk, or remote magnetic tape are collectively referred to as external memory.
It is the great difference in function between the two, which leads to the great difference in the number of reading and writing between them.
When CPU needs to read the data in the hard disk, because the speed of the hard disk is slow and takes a long time, memory will first call out the data from the hard disk, and then let CPU get the data directly into memory to calculate.
However, because the storage medium of the memory is DRAM particles, it uses a transistor plus a capacitor to store one bit (1bit) data.
In other words, DRAM particles rely on capacitors to achieve storage, it needs to replenish the power at regular intervals to preserve data, in other words, the data in memory is only a short stay, once the power off, the capacitor will not work, the data will disappear.
From this point of view, the DRAM particle actually has no physical data to write, which means that it can read and write indefinitely.
But SSD is different, because the storage medium is flash memory particles, it can continue to save data in the event of a power outage.
On the other hand, the flash memory particles have a service life, that is, the number of times to erase and write. Each time the capacity is full, the P / E value is lost, that is, a life is spent. Like human lifespan, subtraction is done from the moment of birth. When several writes exceed the theoretical value, the SSD will be corrupted.
As long as the memory works properly, there is no limit to the number of times to read and write.
SSD has a read and write limit, and the level of the limit is determined according to the type of flash memory.
Seeing here, someone must ask, since memory can be read and written indefinitely, does it mean that memory can be used permanently? The answer is of course not. Apart from the damage caused by man-made external forces, the transistors in DRAM particles will also age over time, which is a problem that all electronic components will face.
All right, that's all for today's popular science. I would also like to remind you here:
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