5-25LESSON 3 CONFIGURING SYSTEM SETTINGSPROFESSIONAL

5-25Lesson 3 Configuring System Settings

Professional. Select System Cache if you are using your computer as a server or if the

programs you are running require a large system cache.

Virtual Memory For virtual memory, Windows XP Professional uses a process called

demand paging to exchange data between random access memory (RAM) and paging

files on the hard disk. When you install Windows XP Professional, Setup creates a

virtual-memory paging file, PAGEFILE.SYS, on the partition in which you installed

Windows XP Professional. The default or recommended paging file size for Windows XP

Professional is equal to 1.5 times the total amount of RAM. For best results, never set

the value of the paging file size to less than the recommended amount. Typically, you

can leave the size of the paging file set to the default value and let Windows XP Pro-

fessional manage the file size. In some circumstances, such as when you run a large

number of applications simultaneously, you might find it advantageous to use a larger

paging file or multiple paging files.

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Exam Tip By default, Windows XP manages the paging file size, but you can designate a

file size for special circumstances. The recommended paging file size is equal to 1.5 times

the total amount of RAM.

To configure the paging file, in the Performance Options dialog box, click the Change

button in the Virtual Memory section. The Virtual Memory dialog box (see Figure 5-10)

identifies the drives in which the paging files reside and allows you to modify the

paging file size for the selected drive.

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Figure 5-10

Configure paging file settings in the Virtual Memory dialog box.

Important Only users with administrative rights can use the Performance Options dialog

box to increase the paging file size.

Paging files never decrease below the value found in the Initial Size text box that was

set during installation. Unused space in the paging file remains available to the internal

Windows XP Professional Virtual Memory Manager (VMM). As needed, a paging file

grows from its initial size to the maximum configured size, which is listed in the Max-

imum Size text box. When a paging file reaches the maximum size, but a running pro-

gram still needs to allocate more virtual memory, Windows XP Professional will refuse

that allocation, which can cause an error, or even a crash, in applications.

When you restart a computer running Windows XP Professional, the system resizes all

paging files to the initial size.

Data Execution Prevention

Data Execution Prevention (DEP) is a set of hardware and software technologies that

perform additional checks on memory to help prevent malicious code from running on

a computer. In Windows XP Professional, DEP can be enforced by compatible hard-

ware and by software.

Note DEP is an update included with Windows XP Service Pack 2. Hardware DEP is avail-

able with compatible devices and runs only on the 32-bit version of Windows XP Professional

and Home Edition.

Hardware DEP works by marking all pages in memory as non-executable unless the

page explicitly contains executable code. This process helps prevent malicious

attacks that try to insert and run executable code into memory. To use hardware DEP,

a computer must have a compatible processor that allows Windows to mark memory

pages as non-executable. Both Intel and AMD provide hardware DEP–compatible

processors.

Software DEP is a set of security checks that can run on any processor capable of run-

ning Windows XP. However, the security provided by software DEP is limited com-

pared to that provided by hardware DEP.

You can configure DEP by using the Data Execution Prevention tab of the Performance

Options dialog box. By default, DEP is enabled for only essential Windows programs

and services. However, you can turn DEP on for all programs and services, and then

select specific programs and services for which you do not want DEP enabled.