1. Storage Technologies and Trends

1.1 Random Access Memory (RAM) p400

• Volatile memory, loses data when powered off
• Types:
  • Static RAM (SRAM): Faster, more expensive, used for cache memory
  • Dynamic RAM (DRAM): Slower, cheaper, used for main memory, requires refresh

1.2 Non-Volatile Memories p404

• Retain data when powered off
• Types:
  • Read-Only Memory (ROM): Programmed during production
  • Programmable ROM (PROM): One-time programmable
  • Erasable PROM (EPROM): Erasable with UV light, reprogrammable
  • Electrically Erasable PROM (EEPROM): Electrically erasable and reprogrammable
  • Flash Memory: Block-level erasable EEPROM, used in SSDs

1.3 Buses p405

• Collection of parallel wires for carrying data, addresses, and control signals
• Types:
  • System Bus: Connects CPU, main memory, and I/O devices
  • Memory Bus: Connects CPU and main memory

1.4 Magnetic Disks p409

• Consist of platters, tracks, sectors, and a read/write head on an arm
• Data accessed by moving arm to correct track and waiting for rotation
• Disk controller maps logical blocks to physical (surface, track, sector) locations

1.5 Solid State Drives (SSDs) p414

• Use flash memory instead of magnetic disks
• Faster, more rugged, and more power-efficient than hard disks
• Wear leveling needed to extend life of flash memory

1.6 Storage Trends

• SRAM, DRAM, and Disk capacity increasing and cost decreasing over time