Dell 3000 Input Errors, Memory-Resident Programs, Program Conflicts, 4. IRQ Line Assignments

Input Errors

If a specific key or set of keys is pressed at the wrong time, a program may give you unexpected results. See the documentation that came with the application program to make sure the values or characters you are entering do not conflict with the application program you are using.

Make sure the operating system is compatible with the programs you use. Keep in mind that whenever you change the parameters of the computer’s operating sys- tem, you may affect the successful operation of the programs. Sometimes, after modifying the operating sys- tem, you may need to reinstall a program that no longer runs properly.

Memory-Resident Programs

There are a variety of utilities and supplementary pro- grams that can be loaded either when the computer boots or from an operating system prompt. These programs are designed to stay resident in system memory and thus always be available for use. Because they remain in the computer’s memory, memory conflicts and errors can result when other programs require use of all or part of the memory already occupied by these TSR programs.

Typically, the operating system’s start-up files contain commands to start TSR programs when you boot the computer. If you suspect that one of these TSR programs is causing a memory conflict, remove the commands that start them from the start-up file. If the problem you were experiencing does not recur, one of the TSR programs probably created the conflict. Add the TSR commands back into the start-up files one at a time until you identify which TSR program is creating the conflict.

Program Conflicts

Some programs may leave portions of their setup infor- mation behind, even though you have exited from them. As a result, other programs cannot run. Rebooting the computer can confirm whether or not these programs are the cause of the problem.

Other programs use specialized subroutines called driv- ers that can cause problems in the computer. For example, a variation in the way the data is sent to an external monitor may require a special screen driver pro- gram that expects a certain kind of video mode or monitor. In such cases, you may have to develop an

alternative method of running that particular program— for example, the creation of a boot file made especially for that program. For help with this situation, call the support service offered by the manufacturer of the soft- ware you are using.

Avoiding Interrupt Assignment Conflicts

Problems can arise if two devices attempt to use the same interrupt request (IRQ) line. To avoid this type of con- flict, check the documentation for the default IRQ line setting for each installed device. Then consult Table 3-4 to configure the device for one of the available IRQ lines.

NOTE: Installed devices cannot share the same COM port address. The default address of the computer’s serial port is COM1.

Table 3-4. IRQ Line Assignments

IRQ Line	Used/Available
IRQ0	Generated by the system timer
IRQ1	Generated by the keyboard controller to
	signal that the keyboard output buffer is
	full
IRQ2	Cascade to second interrupt controller
IRQ3	Reserved
IRQ4	Reserved
IRQ5	Used by the audio controller
IRQ6	Generated by the diskette drive controller
	to indicate that the diskette drive requires
	the attention of the microprocessor
IRQ7	Used by the parallel port
IRQ8	Generated by the system RTC
IRQ9	Software redirect to INT0A
IRQ10	Reserved
IRQ11	Reserved

NOTE: For the full name of an abbreviation or acronym used in this table, see the Glossary in the online System User’s Guide.

3-10 Dell Inspiron 3000 Reference and Troubleshooting Guide