Chpt93 Understanding System Resources

8/9/2019 Chpt93 Understanding System Resources

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Chapter 93Chapter 93

Understanding System Resources


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Slide 2Ver 1.0 10 April 2001

Types of System ResourcesTypes of System Resources

3 typical resources

y IRQ Interrupt Request

y DMA Direct Memory Access

y I/O Port address

y Memory Address

Knowing them is Importance for Detecting and eliminating system

conflicts


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Interrupts (IRQ)Interrupts (IRQ)

Use by devices to demand attention from CPU

Invoke by putting a signal on one of the IRQ line in the bus slot

IRQ 9 is wired to IRQ 2

y Using IRQ 2 is same as using IRQ 9

In ISA, no two devices are allowed to share the same IRQ

y Conflict occurs if more than 1 devices is assigned to same IRQ

y The newly installed device will not work

y Entire system may hang


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IRQ AssignmentsIRQ Assignments

IRQ Functions0 System Timer IC

1 Keyboard Controller IC

2 Second IRQ Controller IC

3 Serial Port2 (COM2: 2F8h-2FFh and COM4: 2E8h-2EFh)

4 Serial Port 1 (COM1: 3F8h-3FFh and COM3: 3E8h-3EFh)

5 Parallel Port 2 (LPT2: 378h OR 278h)

6 Floppy Disk Controller

7 Parallel Port 1 (LPT1: 378h)

8 Real-Time Clock

9 Unused (redirected to IRQ2)

10

USB (on systems so equipped can be disable)11 Windows Sound System

12 PS/2 Mouse

13 Math Coprocessor

14 Primary AT/IDE Hard Disk Controller

15 Secondary AT/IDE Hard Disk Controller


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Direct Memory Access ChannelsDirect Memory Access Channels

Takes over CPUs job of transferring data, without CPU interventiony Between memory location, I/O location

DMA controller on the mainboard

Device requesting DMA transfer starts by signaling the controller

Device must be DMA enabled (through software or BIOS)

Currently only used for low performance devices eg sound card and

floppy drivey Limited to 4Mhz operations

y CPU can transfer data much faster the DMA channel can

Cannot shared DMA channel


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AT DMA AssignmentsAT DMA Assignments

DMA Channel Traditional Function Current Function

0 Dynamic RAM Refresh Audio System

1 Unused Audio system or parallel port

2 Floppy disk controller Floppy disk controller

3 Unused ECP parallel port or audio system

4 Reserved (Internally) Reserved (Internally)

5 Unused Unused

6 Unused Unused


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I/O PortsI/O Ports

Acts like a memory address but its not for storage For the PC to communicate with a device

y Passing of commands and data between the system and expansiondevices

Each device is assigned a I/O port address

Cannot shared I/O port address


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I/O AssignmentI/O Assignment

Address Reserved for170h Secondary IDE Controller channel

1F0h Primary IDE Controller channel

278h LPT2

378h LPT1

3F8h COM1

2F8h COM2

3E8h COM3

2E8h COM4

3F0h Primary Floppy Channel


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Memory AddressMemory Address

Current devices demands memory to support their onboard BIOS ROM(firmware)

y SCSI controllers, network cards, video boards, modem, etc

Memory address cannot overlap


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Pentium PC Memory MapPentium PC Memory Map

Address Range (HEX) Description

100000-10000000 Extended Memory

F0000-FFFFF BIOS

EC000-EFFFF Boot Block (available as UMB)

EA000-EBFFF ESCD (PnP/DMI configuration)

(extended system configuration data)E9000-E9FFF Reserved for BIOS

E8000-E8FFF OEM Logo or Scan User Flash

E0000-E7FFF POST BIOS (available as UMB)

C8000-DFFFF Available High DOS memory

A0000-C7FFF Video memory and BIOS

9FC00-9FFFF Extended BIOS data

80000-9FBFF Extended conventional memory

00000-7FFFF Conventional memory


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Recognising and Dealing with ConflictsRecognising and Dealing with Conflicts

Conflicts almost the result of PC upgrades Recognising Conflict, Use the Last Upgrade Rules:

y A piece of hardware/software has been added to the system veryrecently

y Trouble occurred after a piece of hardware/software was added tothe system

y System was working fine before the hardware/software was added If all three of these common-sense factors are true, chances are that

there is a hardware or software conflict

Confirm and Resolved Conflict, use Last In First Out (LIFO):

y If you install board X and board Y stop to function, board X isprobably conflicting to work properly. Remove board X should

restore board Y to normal operation


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Dealing with Software ConflictsDealing with Software Conflicts

Caused by:

1. TSR (Terminate and Stay Resident)

y Dos programs

y Loads into memory, during initialisation, and waits for a systemevent eg hot key combination

y If suspect to be the problem, find its reference in Autoexec.batand disable it with REM in front of the command eg REMC:\MENU\MENU.EXE)

2. Device Drivers

y Loaded via Config.sys during system initialisation

y If drivers parameters does not match the hardware, thehardware may not work properly

y Disable the driver in the config.sys by placing REM in front of thecommand line eg REM DEVICE=C:\DRIVERS\NEWDRIVE.SYS/A360 /I:5


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Windows Device ManagerWindows Device Manager

Use to inspect configuration and settings of devices in the PC Identify and provide clues that aids trouble-shooting

y Access Device Manager

y Click Start, highlight Setting and click Control Panel

y Double-click the System icon

y Click the Device Manager tab

y Double-click a device type (eg Mouse) to see the devices in thatcategory

y Double-click a device to view its Properties dialog

y In an error code has been generate, the code appears in theDevice Status box on the General tab

Chpt93 Understanding System Resources

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