Computer Memory and Storage

Types of RAM

• Static RAM (SRAM): Faster and more expensive, uses transistors to store data.
• Dynamic RAM (DRAM): Slower and less expensive, uses capacitors to store data.
• Synchronous DRAM (SDRAM): Clock speed synchronized with CPU, improving performance.
• Double Data Rate SDRAM (DDR SDRAM): Transfers data on both rising and falling edges of clock signal.
• Rambus DRAM (RDRAM): High-speed, proprietary technology.

ROM Types

• Mask ROM: Permanently stored data during manufacturing.
• PROM (Programmable ROM): Can be programmed once by the user.
• EPROM (Erasable Programmable ROM): Can be erased and reprogrammed.
• EEPROM (Electrically Erasable Programmable ROM): Can be erased and reprogrammed electrically.
• Flash Memory: A type of EEPROM, used in solid-state drives and memory cards.

Memory Hierarchy

• Level 1 (L1) Cache: Smallest and fastest cache, built into CPU.
• Level 2 (L2) Cache: Larger and slower than L1, usually located on the CPU.
• Level 3 (L3) Cache: Shared among multiple CPUs in a multi-core system.
• Main Memory: Larger and slower than cache, where data is stored.
• Secondary Storage: Slowest and largest, where data is stored on devices like hard drives.

Cache Memory

• Cache Hit: When the CPU finds the required data in the cache.
• Cache Miss: When the CPU does not find the required data in the cache.
• Cache Replacement Policies: Strategies to replace cache lines, such as LRU (Least Recently Used) and FIFO (First-In-First-Out).
• Cache Line: A block of data transferred between cache and main memory.

Virtual Memory

• Virtual Address Space: The range of addresses a process can use.
• Physical Address Space: The actual addresses available in physical memory.
• Page Table: A data structure that maps virtual addresses to physical addresses.
• Page Fault: When a process accesses a page not in physical memory, causing a page fault.
• ** Paging**: The process of transferring pages between physical memory and secondary storage.