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Memory, better known as Random Access Memory (RAM) is a set of chips used to store information. These chips can only store information as long as there is electrical power. When the power is turned off, they 'forget' everything and all data is lost. This is because the RAM uses the electricity to store the information. When the electricity dies, so does your data.

Memory comes in a number of configurations for IBM compatible PC's. Memory also comes in parity checking vs. non-parity checking. Parity checking is verifying that there is an even or odd number of 1's or zeroes in the data set. This means that memory that does parity checking is able to verify that it is functioning correctly when running. Most memory sold today is non-parity RAM, and is only checked for errors on start up by writing to and reading from every location in memory.

Memory Types

Read-Only Memory

• BIOS
• CMOS

Eraseable / Programmable Read-Only Memory (EPROM/EEPROM)

DRAM - Dynamic Random Access Memory - Needs Refresh

• FPM - Fast Page Memory
• EDO - Extended Data Out
• DDR - Dual Data Rate (DDR2, DDR3, DDR4, DDR5)

SDRAM - Synchronous Dynamic Random Acess Memory (DIMMs)

• PC66 @ 66 Mhz or 100 Mhz
• PC100 @ 125 Mhz
• PC133 @ 133 Mhz or 143 Mhz

DDR SDRAM - Double / Dual Data Rate SDRAM (DIMMs)

• DDR200 / PC1600 @ 100 Mhz
• DDR266 / PC2100 @ 133 Mhz
• DDR333 / PC2700 @ 166 Mhz
• DDR400 / PC3200 @ 200 Mhz
• DDR433 / PC3500 @ 217 Mhz
• DDR466 / PC3700 @ 233 Mhz
• DDR500 / PC4000 @ 250 Mhz
• DDR 550 / PC4400 @ 275 Mhz
• DDR 600 / PC4800 @ 300 Mhz

DDR2 / PC2

• DDR2 - 400 / PC2 - 3200 @ 100 Mhz
• DDR2 - 533 / PC2 - 4200 @ 133 Mhz
• DDR2 - 667 / PC2 - 5300 @ 166 Mhz
• DDR2 - 800 / PC2 - 6400 @ 200 Mhz
• DDR2 - 1000 / PC2 - 8000 @ 250 Mhz

DDR3 / PC3

• DDR3 - 800 / PC3 - 6400 @ 100 Mhz
• DDR3 - 1066 / PC3 - 8500 @ 133 Mhz
• DDR3 - 1333 / PC3 - 10667 @ 166 Mhz
• DDR3 - 1600 / PC3 - 12800 @ 200 Mhz
• DDR3 - 1866 / PC3 - 14900 @ 250 Mhz
• DDR3 - 1866 / PC3 - 15000 @ ??? Mhz
• DDR3 - 2133 / PC3 - 17000 @ ??? Mhz

DDR4

SRAM - Static Random Access Memory

• No Refresh
• Used in Cache Memory (L1 Cache, L2 Cache, L3 Cache)

RDRAM - RAMBUS Dynamic Random Access Memory (RIMM)

• 16-bit
  • RIMM 1600 / PC800 @ 400 Mhz
  • RIMM2100 / PC1066 @ 533 Mhz
  • RIMM2400 / PC1200 @ 600 Mhz
• 32-bit RDRAM
  • RIMM3200 / PC 800 @ 400 Mhz
  • RIMM4200 / PC1066 @ 533 Mhz
  • RIMM4800 / PC1200 @ 600 Mhz

RAM / Memory Form Factors

• Desktop, Workstation and Server RAM / Memory Form Factors
  • SIMMS - Single In-line Memory Module (obsolete)
    • Pinouts:
      • 30-pin (8 bits + 1 parity bit)
      • 72-pin (32 bits plus optional 4 parity bits)
    • Types Supported
      • Fast Page Mode (FPM) DRAM
      • Extended Data Out (EDO) DRAM
  • DIMMS - Dual Inline Memory Module
    • Pinouts
      • 168-pin SDRAM
      • 184-pin DDR SDRAM
      • 240-pin DDR2 SDRAM
  • RIMM - "RAMBUS" Inline Memory Module
    • Pinouts
      • 184-pin
      • 232-pin
• Laptop RAM / Memory Form Factors
  • Micro DIMM
    • 144-pin
    • 172-pin
    • 214-pin
  • SO-DIMM - Small Outline DIMM
    • 72-pin
    • 144-pin
    • 200-pin
    • 204-pin

Virtual Memory

• Local Storage
• Pagefile
• Scratch memory

RAM / Memory Architecture

• Memory Controller Hub
• Memory Banks (not sides)
  • Single Bank
  • Dual Bank
• Memory Channels
  • Single Channel
  • Dual Channel
• System Bus
• Buffers
• Nonparity, Parity and ECC

Memory Layout

• Upper Memory Area (UMA)
  • Video RAM Memory
  • Adapter ROM
  • Motherboard ROM BIOS
• Extended Memory
• Protected Mode (RAM above the first 1 MB)