Types of Main Memory: RAM vs. ROM, Cache Memory, and Virtual Memory, Lecture notes of Technology

Download Types of Main Memory: RAM vs. ROM, Cache Memory, and Virtual Memory and more Lecture notes Technology in PDF only on Docsity! 1 Types of main memory; The memory unit can be implemented using a variety of memory chips- different speeds, different manufacturing technology, and different sizes. The main memory types are: 1- Read Only Memories (ROM): ROMs allow only read operation to be performed. This memory is non-volatile. Most ROMs are programmed and cannot be altered. This type of ROM is cheaper to manufacture than other types of ROM. The program that controls the standard I/O functions (called BIOS) and configuration software are kept in ROM,. Other types of ROM include: A- Programmable ROM (PROM). B- Erasable PROM (EPROM) is read only memory that can be reprogrammed using special equipment. C- EAPROM, Electrically Alterable Programmable ROM is a Read Only Memory that is electrically reprogrammable. 2- Read/Write Memory (RAM):- Read/Write memory is commonly referred to as Random Access Memory (RAM), it is divided into static and dynamic. A-Static RAM (SRAM): used for implementing CPU registers and used for special high speed memory called cache memory this greatly improves system performance. Static RAM keeps its value without having to be refreshed. B-Dynamic RAM (DRAM), the bulk of main memory in a typical computer system consists of dynamic Ram. DRAM is where programmed, data are kept when a program is running. It must be refreshed with in less than a millisecond or losses its contents. 2 The differences between RAM AND ROM NOTE: The Main Memory is called also primary memory or primary storage RAM ROM 1-Stand foe Random - Access memory 1- stand for Read Only Memory 2- Read /Write memory 2-READ Only Memory 3-Sending data (writing) to RAM memory address is called destructive write because the new data erases whatever was there before 3-Sending data to ROM memory address is in effective because the contents of ROM can not changed (write not allowed ) because this memory for read only 4-form of primary storage(main memory) for holding temporary data and instruction 4-form of primary storage(main memory) for holding permanent data and instruction 5- Volatile : program and data are erased when the power is off 5-Permanent : program and data are intact even power is off 6- Type of RAM is a- Static RAM b- Dynamic RAM 6-Type of ROM is a- PROM b-EPROM c- EAPROM