RAM and ROM Memory Overview

Introduction

Types of Memory

RAM Memory

ROM Memory

Hybrid Memory

Types of Memory

RAM Memory

SRAM-Static Random-Access Memory

DRAM - Dynamic Random-Access Memory

SRAM

SRAM Internal Structure

SRAM Memory

Fastest type of memory

Low density

More expensive

Generally used in small amounts (L2 cache) or expensive servers

DRAM Memory

DRAM Internal Structure

Types of DRAM

SDRAM - Synchronous dynamic RAM

DDR RAM - Double data rate RAM

DDR2 RAM

DDR3 RAM

DDR4 RAM

DRAM Memory Very high density

Cheap data cache in computers

Must be periodically refreshed

Slower than SRAM

Volatile

DDR Internal Structure

Row 1 Row 2 Row 3 Row 40

2

4

6

8

10

12

Column 1Column 2Column 3

DDR2 Internal Structure

DDR3 Internal Structure

DDR Comparison

DDR3 and DDR4 Review

DDR4 Memory

SRAM Memory Interface

SDRAM Memory Interface

DDR Memory Inreface

SRAM vs DRAM

SRAM is faster compared to DRAM

SRAM consumes less power than DRAM

SRAM uses more transistors per bit of memory compared to DRAM

SRAM vs DRAM Cont.

SRAM is more expensive than DRAM

Cheaper DRAM is used in main memory while SRAM is commonly used in cache memory

DRAM Required Refresh cycle

DRAM Required EDC Circuit

ROM Memory

Mask ROM - Mask Read Only Memory

PROM - Programmable Read Only Memory

EPROM - Erasable Programmable Read Only Memory

PROM Memory

ROM Memory

Programmable by special program tools/modes

Read only memory during normal use

Non-volatile

EPROM uses UV light to reset all bits

Hybrid Memory

Flash Memory

NVRAM - Non-volatile random-access memory

EEPROM - Electrically Erasable Programmable Read-Only Memory

Flash Memory

NAND Flash Memory

NOR Flash Memory

Flash Memory Architecture

NAND Flash Memory

NAND Flash

NAND vs NOR Flash

NAND and NOR Pins

Selection Check Point Most writes must be preceded by an erase

operation

NAND has smaller erase units for fewer erases in less time

NOR is an XIP device

NAND Flash Memory

NAND Flash

NAND Flash

NAND Memory Interface

Memory Mapping in NOR Flash

NOR Flash Interface

Memory Mapping in NOR Flash

Any Questions

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