1.0 Hardware

1.6 Compare and contrast memory types, characteristics and their purpose

  • Types
    • DRAM

      • Dynamic Random Access Memory
      • Needs refreshing

    • SRAM

      • Static Random Access Memory
      • Frequently used in processors
      • Does not need refreshing
      • More expensive and faster than DRAM

    • SDRAM

      • Synchronized Dynamic Random Access Memory
      • Runs on clock speeds
      • 3.3 volts
      • 168 pins

    • DDR

      Double data rate is a type of SDRAM in which data is sent on both the rise and fall of the clock cycle.

      • Twice as fast as SDRAM
      • Also refered to as "Double Pumping"
      • 2.5 volts
      • 184 pins

    • DDR2

      • Twice as fast as DDR
      • 240 pin DIMM

    • DDR3

      • Four times as fast as DDR
      • 240 pin DIMM

    • RAMBUS

      • Designed by Rambus, Inc.
      • Modules known as RIMM (Rambus Inline Memory Module)
      • Current use is limited
      • Equipped with heat shields
      • Runs at a multiplier of clock speed
      • Reads data on both rise and fall of clock cycle
      • 184 pins
      • Installed in pairs
      • Requires a module called CRIMM for open slots

  • Parity vs. Non-parity
    • Parity

      • Uses an additional chip for parity
      • Higher cost due to additional chips
      • Cannot correct, but can detect errors

    • Non-parity

      • Has fewer chips
      • Does not need to calculate parity
      • Non-parity systems have no fault tolerance

  • ECC vs. non-ECC
    What's the Difference? (Video by CrucialMemory)

    • ECC

      • Error Correcting Code
      • Capable of detecting and correcting errors
      • Used in high-end systems
      • Motherboard must support ECC

    • Non-ECC

      • Is not capable of correcting errors

  • Single sided vs. double sided
    Refers to memory ranks or groupings
    Not a reference to the physical sides of memory modules

    • Single sided

      Refers to a single rank of chips in which the computer can access all at once.

    • Double sided

      • A type of memory in which its chips are divided into two ranks
      • Only one rank can be accessed at a time
      • Access must switch from one rank to the other and back again

  • Single channel vs. dual channel

    • Single channel

      • Memory controller can only access one module at a time

    • Dual channel

      • Requires a motherboard capable of dual-channel technology
      • Requires two or more memory modules
      • Best to use identical pairs of memory modules
      • Memory banks are typically color-coded

  • Speed
    • PC100

      • 100 MHz clock speed
      • 168-pin DIMM form factor
      • 144-pin SO-DIMM for laptops
      • 3.3 volts

    • PC133

      • 133 MHz clock speed
      • 168-pin DIMM form factor
      • 168-pin SO-DIMM for laptops
      • 3.3 volts

    • PC2700

      • DDR-333
      • 166 MHz clock speed
      • 184-pin DIMM form factor
      • 200-pin SO DIMMS or 172-pin micro-DIMMS for laptops
      • 3.3 volts

    • PC3200

      • DDR-400
      • 200 MHz clock speed
      • 184-pin DIMM form factor
      • 200-pin SO DIMMS or 172-pin micro-DIMMS for laptops

    • DDR3-1600

      • PC3-12800
      • 200 MHz clock speed
      • 240-pin DIMM form factor
      • 204-pin SO DIMM for laptops
      • 1.5 volts

    • DDR2-667

      • PC2-5300
      • 133 MHz clock speed
      • 240-pin DIMM form factor

I've gathered some additional free resources for those that prefer to mix video tutorials in with their study routine.

Professor Messer's
CompTIA A+ Training Course

All of Professor Messer's CompTIA A+ training videos are completely free when you view them online.

An Overview of Memory

Identifying Memory Types

A+ All-In-One
LearnSmart Video Training Preview
- Memory -

Free preview of LearnSmart Video Training. Try this online preview and you'll experience a complete 30 minute portion of the LearnSmart Video Training course.

VTC Flexible Learning Demo

(Requires QuickTime)

  1. Memory Basics
  2. Types of RAM
  3. Types of DRAM (part 1)
  4. Types of DRAM (part 2)
  5. RAM Characteristics