Context

• Memory operations slower than arithmetic
  • add, sub, shift: 1 cycle
  • mult: 3 cycles
  • load/store: 100+ cycles
• Modern computers are memory bottlenecked

Characteristics of Memory

<aside> ℹ️ Computer Memory: Any physical device capable of storing information

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Memory Categories:

• SRAM (Static Random Access Memory)
• DRAM (Dynamic Random Access Memory)
• PROM (Programmable Read-Only Memory)
• Magnetic Disk

Access methods:

• Sequential Access:
  • organized into records, accessed in sequence (e.g., magnetic tape)
• Direct/Random Access:
  • Each location has a unique address,
  • Access time independent of prior accesses (e.g., main memory, cache)

Measures of Performance:

• Access Time (latency): time to perform a read or write operation
• Memory Cycle Time: access time + cooldown (before additional access can be made)
• Transfer Rate: $\frac{1}{\text{memory cycle time}}$ (unit: MT/s - million transfer per sec)

Memory Hierarchy

Basics