memory COMPUTER ORGANIZATION – ITC04 1

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CPU (processing) Random Access Memory RAM Temporarily holds Data or Instruction 3

RAM CATEGORIES DRAM (Dynamic RAM)  Is used for a memory cache  Cache – makes the data used most often by the CPU instantly available  Primary / Level 1  Secondary / Level 2 SRAM (Static RAM)  Is called that (SRAM) because it holds its data as long as the RAM has power. 4

DRAM – Dynamic Random Access Memory  Loses its data rapidly, and the memory controller must refresh it several thousand times a second.  Volatile Memory.  Stored in memory modules, which are installed in memory slots on the motherboard. 5

Memory Module  DIMM (dual inline memory module)  SO-DIMM (small outline DIMM and pronounced “sew- dim”)  MicroDIMMs  RIMM (rambus inline memory module) Rambus, Inc.  SIMM (single inline memory module) The major differences among these modules are the width of the data path that each type of module accommodates and the way data moves from the system bus to the module 6

Types of memory modules  240-pin DDR3 DIMM is currently the fastest memory. It can support triple or dual channels or be installed as a single DIMM. It has an offset notch farther from the center than a DDR2 DIMM. 7

Types of memory modules  240-pin DDR2 DIMM can support dual channels or be installed as a single DIMM. Has one notch near the center of the edge connector. 8

Types of memory modules  184-pin DDR DIMM can support dual channels or be installed as a single DIMM. Has one offset notch. 9

Types of memory modules  168-pin SDRAM DIMM has two notches on the module. The positions of these notches depend on the memory features the DIMM uses. 10

Types of memory modules  RIMM has 184 pins and two notches near the center of the edge connector. 11

Types of memory modules  72-pin SIMM must be installed two modules to a bank of memory. 12

Types of memory modules  30-pin SIMM must be installed four modules to a bank of memory. 13

Timeline of memory technologies 14

DIMM TECHNOLOGIES  64-bit data path  Independent pins on opposite sides of the module.  did not run in sync with the system clock  Their speeds are measured in nanoseconds (ns)  The first DIMM to run synchronized with the system clock was synchronous DRAM (SDRAM), which has two notches, and uses 168 pins. 15

DIMM TECHNOLOGIES  Double Data Rate SDRAM (DDR SDRAM, or SDRAM II, or simply DDR) is an improved version of SDRAM.  DDR runs twice as fast as regular SDRAM, has one notch, and uses 184 pins.  DDR2 is faster and uses less power than DDR.  DDR3 is faster and uses less power than DDR2.  Both DDR2 and DDR3 use 240 pins 16

SIMM TECHNOLOGIES  are rated by speed, measured in nanoseconds (ns)  60, 70, or 80 ns. 17

Two major categories of SIMMs  72-pin SIMMs - use a data path of 32 bits  30-pin SIMMs - use a 16-bit address bus 18