BUS Configurations
Handling Interrupt Requests
Objectives:
To describe some of the main bus technologies and configurations, and to discuss
the plug-and-play systemDiscuss the function of buses
Describe the most common bus standards available
Outline how buses typically relate to one another in a modern PC
Outline the concept and the practicalities of the plug-and-play system
Review:
You have seen BIOS configuration, physical memory, and interrupt request handling.
The system BIOS is the interface between the processor and the operating system
on a PC.It also allows the user to control hardware settings and it is responsible for booting up the machine when it is turned on.
BIOS settings are traditionally stored in a special nonvolatile type of memory called CMOS.
The BIOS is refreshed by a battery, which ensures that any data stored in it will not be lost when the PC is switched off. More recent BIOSes use flash memory.
There are several standard BIOS settings andsome advanced settings that are specific to particular BIOS brands.
Some of the standard settings include the system date, the system time,the floppy disk types, and the hard disk types.
Read-only memory (ROM) is a type of memory that can only be read, but not written to. It is nonvolatile and reasonably secure.
There are several variants on ROM, some of which are more flexible than regular ROM.
Random-access memory (RAM) is memory that can be read and written to. It is much more volatile than ROM - the contents of RAM are lost when a machine is powered off.
RAM is much faster than ROM.
A DIMM is a dual in-line memory module, while a SIMM is a single in-line memory module.
Both of these provide a path to memory for the processor. A DIMM provides a path which is twice as wide as that provided by a SIMM.
Extra DIMMs and SIMMs can be installed on a motherboard to improve the performance of a PC.
The correct socket must be identified and the memory modules carefully slotted into place.
Interrupts use a processor's resources more efficiently than polling.
Devices in a PC can generate an interrupt to get the processor's attention only when they need it.
Maskable interrupts can be ignored by the processor if it is in the middle of a particular task, but nonmaskable interrupts must be attended to immediately.
There are different defaults and common uses for interrupt request lines, which are numbered from 0 to 15.