Dell Latitude XPi CD Průvodce řešením problémů stáhnout pdf (Strana 56)

3-16 Dell Latitude XPi CD Reference and Troubleshooting Guide

Memory Allocations

A microprocessor and programs operating under

MS-DOS (real-mode operation) can address only

1 megabyte (MB) (1024 kilobytes [KB]) of system mem-

ory. This area is divided into conventional memory

(sometimes called base memory) and upper memory. All sys-

tem memory above this 1 MB is called extended memory and

cannot be directly addressed by MS-DOS–based programs

without the aid of some special memory-managing software.

Table 3-5 provides a map of the conventional memory area.

When the microprocessor or a program addresses a location

within the conventional memory range, it is physically

addressing a location in main memory, which is the only main

memory it can address under MS-DOS.

Table 3-6 provides a map of the upper memory area. Some of

these addresses are dedicated to various system devices, such

as the system/video basic input/output system (BIOS). Others

are available for use by expansion cards and/or an expanded

memory manager (EMM). When the microprocessor or a pro-

gram addresses a location within the upper memory area, it is

physically addressing a location within one of these devices.

IRQ12 Generated by the keyboard controller

to indicate that the output buffer of the

integrated trackball or external PS/2

mouse is full

IRQ13 Not available

IRQ14 Generated by the hard-disk drive to

indicate that the drive requires the

attention of the microprocessor

IRQ15 Reserved for the CD-ROM drive

Table 3-4. IRQ Line Assignments

(Continued)

IRQ Line Used/Available

NOTE: For the full name of an abbreviation or acronym used

in this table, see the Glossary in the online System User’s

Guide.

Table 3-5. Conventional Memory Map

Address Range Use

00000h–003FFh Interrupt vector table

00400h–004FFh BIOS data area

00500h–005FFh MS-DOS and BASIC work area

00600h–0FFFFh User memory

10000h–1FFFFh User memory

20000h–2FFFFh User memory

30000h–3FFFFh User memory

40000h–4FFFFh User memory

50000h–5FFFFh User memory

60000h–6FFFFh User memory

70000h–7FFFFh User memory

80000h–8FFFFh User memory

90000h–9FBFFh User memory

NOTE: For the full name of an abbreviation or acronym

used in this table, see the Glossary in the online System

User’s Guide.

1 2 ... 51 52 53 54 55 56 57 58 59 60 61 ... 147 148

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