Computer Memory Basics

Computer Memory

RAM (Random Access Memory)

• Volatile memory technology, meaning contents are lost when power is turned off
• Temporary storage for data and program instructions currently being used by CPU
• Data can be read and written quickly
• Capacity measured in bytes (KB, MB, GB, etc.)
• Divided into:
  • Static RAM (SRAM): faster, more expensive, and less dense
  • Dynamic RAM (DRAM): slower, less expensive, and more dense

ROM (Read-Only Memory)

• Non-volatile memory technology, retaining data even when power is off
• Permanent storage for data and program instructions
• Data can only be written once during manufacturing, then becomes read-only
• Used for firmware, bootloaders, and other persistent data

Cache Memory

• Small, fast, and expensive memory built into CPU
• Acts as buffer between main memory and CPU, reducing access time
• Divided into levels (L1, L2, L3, etc.), each with decreasing size and access time
• Optimizes performance by storing frequently accessed data

Memory Hierarchy

• Organization of memory systems in a computer, from fastest to slowest:
  1. Registers (inside CPU)
  2. Cache
  3. Main Memory (RAM)
  4. Secondary Storage (hard drives, SSDs, etc.)
  5. Tertiary Storage (tapes, optical discs, etc.)
• Each level acts as a cache for the next, reducing access time and improving performance

Virtual Memory

• Combination of physical RAM and secondary storage (hard drive) to provide more memory
• Operating system manages virtual memory, swapping pages of memory to and from disk as needed
• Provides larger address space than physical RAM, allowing for more programs to run
• Page Fault occurs when CPU requests a page not in physical RAM, causing a delay while the page is retrieved from disk

Computer Memory

RAM (Random Access Memory)

• Volatile, meaning data is lost when power is turned off
• Temporary storage for data and program instructions currently used by CPU
• Data can be read and written quickly
• Capacity measured in bytes (KB, MB, GB, etc.)
• Divided into two types:
• Static RAM (SRAM): faster, more expensive, and less dense
• Dynamic RAM (DRAM): slower, less expensive, and more dense

ROM (Read-Only Memory)

• Non-volatile, retaining data even when power is off
• Permanent storage for data and program instructions
• Data can only be written once during manufacturing, then becomes read-only
• Used for firmware, bootloaders, and other persistent data

Cache Memory

• Small, fast, and expensive memory built into CPU
• Acts as a buffer between main memory and CPU, reducing access time
• Divided into levels (L1, L2, L3, etc.), each with decreasing size and access time
• Optimizes performance by storing frequently accessed data

Memory Hierarchy

• Organization of memory systems in a computer, from fastest to slowest:
• Registers (inside CPU)
• Cache
• Main Memory (RAM)
• Secondary Storage (hard drives, SSDs, etc.)
• Tertiary Storage (tapes, optical discs, etc.)
• Each level acts as a cache for the next, reducing access time and improving performance

Virtual Memory

• Combination of physical RAM and secondary storage (hard drive) to provide more memory
• Operating system manages virtual memory, swapping pages of memory to and from disk as needed
• Provides larger address space than physical RAM, allowing for more programs to run
• Page Fault occurs when CPU requests a page not in physical RAM, causing a delay while the page is retrieved from disk