PROM is a programmable ROM, but it can be programmed once only, that is, after the software is written, it cannot be modified. ROM usually refers to solidified computer memory (write once, read repeatedly), which is opposite to the RAM.
Moreover, its row and column addresses are multiplexed, and many have page mode. DRAM (dynamic random access memory) requires constant refresh to save data. SRAM (static random access memory) does not need to be refreshed when power is applied, that is, data will not lost, and is generally not multiplexed with row and column addresses. DRAM keeps data for a short time and slower than SRAM, but it is faster than any ROM, but DRAM is cheaper than SRAM in terms of price. SRAM is very fast, in other words, it is the fastest storage device for reading and writing, but it is also very expensive. So it is only used in demanding places, the primary buffer or secondary buffer of CPU, for example. There are two main types of RAM, one is called static RAM ( SRAM). It is characterized by nonvolatile, that is, power loss then memory loss. Such a memory will lose its storage contents when the power is turned off, therefore, it mainly used to store programs for short-term use. The contents of the storage unit can be freely taken out or stored as needed. It is now used in computer systems as external storage. The optical disk storage uses a laser to read on a magneto-optical material, which is non-volatility with good durability and high recording density. The feature is that non-volatile, the data will not disappear after power-off, and the access speed is slow. A layer of magnetic material is coated on metal or plastic to store data. What’s more, when the power is lost, the stored data is also lost, which is a kind of volatile memory.Ī computer memory made of magnetic material is called a magnetic memory. The following expreessed are the key characteristics of main computer memories.Ī computer memory composed of a semiconductor is called a semiconductor memory, and the memory of the semiconductor is small in size, low in power, and short in access time. Ⅳ Main Technical Indicators of Computer Memory
Catalogģ.3 Differences between MASK ROM,FALSH ROM and OTP ROM Different Types of Computer Memory Characteristics in Microprocessor Has Been Discussed in this Video.