Introduction to Computing Lecture-06-Primary Memory Muhammad Hafeez Department of Computer Science GC University Lahore

Today’s Agenda RAM Types of RAM

Primary Memory Stores three categories of items: 1. Operating System 2. Application Programs 3. Data used by application Programs Role of primary memory to store both data and information is called stored program concept.

Primary Memory Data loaded in primary memory in bytes Each byte is stored at a unique location in the primary memory Hence, primary memory is called a byte-addressable memory To access data and instructions memory the computer reference the address

Random Access Memory The processor read/ write data from RAM The data is loaded in RAM from permanent storage such as Hard Disk Drives Data stored in RAM is volatile. Types of RAM Two most common types of RAM are: Dynamic RAM (DRAM) Static RAM (SRAM)

Random Access Memory DRAM: This type of RAM has to be reenergized constantly, otherwise it loses its content, many types of DRAM variations exists SRAM: SRAM do not need to be reenergized more often, hence, they are more reliable. SRAM are faster than DRAM also much more expensive. Special application of SRAM are cache, registers

Variations of DRAM

Memory Bandwidth A rate in which the data can be read/ write from/to RAM to processor For example, a computer with dual-channel memory and one DDR2-800 module per channel running at 400 MHz would have a theoretical maximum memory bandwidth of=400,000,000 clocks per second × 2 lines per clock × 64 bits per line × 2 interfaces =102,400,000,000 (102.4 billion) bits per second (in bytes, 12,800 MB/s or 12.8 GB/s)

Memory Bandwidth A rate in which the data can be read/ write from/to RAM to processor For example, a computer with dual-channel memory and one DDR2-800 module per channel running at 400 MHz would have a theoretical maximum memory bandwidth of=400,000,000 clocks per second × 2 lines per clock × 64 bits per line × 2 interfaces =102,400,000,000 (102.4 billion) bits per second (in bytes, 12,800 MB/s or 12.8 GB/s)

Memory Slots SIMM: Single in-line Memory Module Same types of connector on both sides Old, legacy systems DIMM: Dual in-line Memory Module Different types of connectors on both sides Most common type

Cache Memory A fast SRAM in a limited capacity on motherboard that is used to frequently used instructions/ data it also minimize processor/ memory speed mismatch. Types of Cache Memory L1 Cache L2 Cache L3 Cache

Cache Memory L1 Cache L2 Cache L3 Cache Directly built on processor, available in small capacity L2 Cache Slightly larger than L1 cache, ATC (Advance Transfer Cache) directly built on processor L3 Cache Available on motherboard, used on processor that use ATC cache How processor search data/ information ?

Cache Memory

Machine Instruction Cycle

Machine Instruction Cycle

Machine Instruction Cycle Fetch: Instruction fetch Decode: Pass ALU the signal to process the instruction Fetch Operands: send read signal to memory to read operands Execute: Instruction is processed with the contents of DR/AC Store: Result is stored in RAM with write signal

ROM (Read Only Memory) A non-volatile memory to store permanent data that cannot be modified necessary for the operation of computer especially startup. Most peripheral devices/ mobile devices also contains ROM chips i.e. printer has ROM chips to store Font data Manufacturers of the electronic machines write permanent data/ instructions in ROM Chips that also called Firmware. Types of ROM EPROM, EEPROM

CPU Internal Architecture

Memory Hierarchy

Registers A processor contains small, high-speed storage locations for temporary data/ information storage. There are many types of registers, some perform specific task like controlling the functions others perform more general tasks.

Adapters Cards/ Expansion Slot/ Port Adapter card is an electronic circuit board that enhances the functionality of a computer Expansion slot is socket on motherboard that can hold an adapter card PCI (Peripheral Component Interconnect) PCI-Extended PCI-Express A port provides interface between peripheral devices and motherboard

Motherboard/ Adapter Cards/ Expansion Slots

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