RAM, CPUs, & BUSESEgle Cebelyte

What is RAM?

Random Access Memory is simply the storage area where all software is loaded and works from; also called working memory storage.

DRAM- Dynamic Random Access Memory◦ More common type◦ Needs to be refreshed constantly

SRAM- Static Random Access Memory◦ Faster◦ More expensive

Rambus RAM◦ Advanced RAM, only used for very few Pentium

4’s DDR RAM

◦ A faster version of SD RAM, which is an older type

RAM Types

RAM speed is measured in ns (nano seconds) The fewer ns, the faster is the RAM The more MB of RAM, the faster your PC

RAM Speeds

Clock speed

Time per clock tick

20 MHz 50 ns

25 MHz 40 ns

33 MHz 30 ns

50 MHz 20 ns

66 MHz 15 ns

100 MHz 10 ns

133 MHz 6 ns

CPU- Central Processing Unit◦ Two main functions- 1) calculating and 2) moving

data◦ The faster the CPU, the faster your PC

CPU

The CPU consists of millions of transistors. The transistors are connected by electronic

tracks. The narrower the tracks, the more

transistors can be added to the CPU; hence, the speed of the CPU is increased.

In 1965, Gordon Moore predicted that the number of transistors in processors would be doubled every 18 months.

Moores’ Law

ALU- the arithmetic logic unit◦ Performs arithmetic and logical operations

CU- the control unit◦ Extracts instructions from memory, decodes and

executes them, calling on the ALU when necessary

CPU Components

Instruction set◦ The set of instructions that the microprocessor

can execute Bandwidth

◦ The number of bits processed in a single instruction

Clock speed◦ Given in megahertz (MHz). The clock speed

determines how many instructions per second the processor can execute.

Characteristics of CPUs

A bus is a collection of wires through which data is transmitted from one part of a computer to another.

Two main types of buses- the system bus and the I/O buses.

Buses

Connects the CPU with RAM and L2- cache Central bus

System bus

Move data Connect all I/O devices with the CPU and

RAM Main types of I/O buses

◦ ISA bus◦ PCI bus◦ USB bus◦ AGP bus

I/O Buses

Questions?