Dell Precision 420 - Manual (Page 124)

Program Conflicts
Some programs may leave portions of their setup information behind, even though you have exited from them. As a result, other programs cannot
run. Rebooting your system can confirm whether or not these programs are the cause of the problem.
Programs that use specialized subroutines called device drivers can also cause problems with your computer system. For example, a variation in
the way the data is sent to the monitor may require a special screen driver program 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
—the creation of a boot file made especially for that
program, for example. Call the support service for the software you are using to help you with this problem.
Memory Address Conflicts
Memory address conflicts occur when two or more devices try to access the same address in the upper memory blocks (UMB). For example, if a
network expansion card and an expanded-memory page frame are assigned an overlapping block of addresses, a memory address conflict
arises. As a result, when you try to log in to the network, the operation fails.
To resolve this type of conflict, you can change the address of one of the devices. For example, in the case of the network expansion card and
expanded-memory page-frame address conflict, you can move the network card to an address block in the range of CC000h through D0000h. To
reassign the expansion card's address block, refer to the documentation for the card.
Interrupt Assignment Conflicts
Problems can arise if two devices attempt to use the same interrupt request (IRQ) line. To avoid this type of conflict, check the documentation for
the default IRQ-line setting for each installed expansion card. Then consult
Table 1 to configure the card for one of the available IRQ lines.
Table 1. Default IRQ Line Assignments
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IRQ Line Used/Available
IRQ0 Used by the system timer
IRQ1 Used by the keyboard to signal that the output buffer is full
IRQ2 Used by interrupt controller 1 to enable IRQ8 through IRQ15
IRQ3 Used by serial port 2
IRQ4 Used by serial port 1
IRQ5 Available
IRQ6 Used by the diskette/tape drive controller
IRQ7 Used by the parallel port
IRQ8 Used by the real-time clock (RTC)
IRQ9 Available
IRQ10 Available
IRQ11 Available
IRQ12 Used by the mouse port
IRQ13 Used by the math coprocessor (if applicable)
IRQ14 Used by the primary integrated drive electronics (IDE) controller
IRQ15 Used by the secondary IDE controller