3.4. Objective 5: Set Up Different PC Expansion Cards

As described in Objective 1, when you add hardware to a PC you must accommodate the resource requirements of all installed devices. Your requirements will depend on the type of card, such as whether it is Industry Standard Architecture (ISA) or PCI. This Objective covers the technical details you are required to understand when configuring these types of devices.

3.4.1. Plug and Play

Older hardware, particularly ISA bus hardware, requires manual configuration. Exam 102 requires familiarity with these configuration problems.

Generally speaking, we may think about device configuration methodologies from one of three general eras:

Jumper era

This hardware was constructed in such a way that settings were controlled by changing the position of shorting jumpers on terminal strips. This method is inconvenient in that it requires internal access to the PC as well as available documentation on the jumper locations. On the other hand, it is a hardware-only solution, and the settings are obvious to the observer. Many such devices are still in service on older PCs.

Nonvolatile era

These more recent hardware designs abandoned jumpers in favor of settings that, while still manually set, are stored in a nonvolatile memory space. This design eliminated the physical access problem with jumpered hardware, but introduced a requirement that custom configuration programs be written, supported, and provided to consumers by hardware vendors. This software was almost always based on MS-DOS. Using these configuration tools to program a card for use under Linux may require a working MS-DOS machine to provide initial configuration.

Modern era

Most recent cards work with the PCI bus to automatically configure themselves. The settings are done during system initialization, prior to loading the operating system. This automation eliminates manual configuration and frees the user from worrying about device conflicts.

To configure an older device, you may need to set jumpers or possibly run MS-DOS and a proprietary configuration utility. More often than not, factory default settings can be used with the Linux networking drivers. However, once manual configuration is accomplished, you'll need to be sure that you don't have conflicts with IRQs, I/O addresses, and possibly DMA channel assignments.

3.4.1.1. Using the /proc filesystem

When adding new hardware to an existing Linux system, you may wish to verify which resources the existing devices are using. The /proc filesystem, the kernel's status repository, contains this information. The proc files, interrupts, dma, and ioports, show how system resources are currently utilized. (These files may not show devices unless their device files/drivers are open/active. This may make the problem harder to find if you're experiencing resource conflicts.) The following is an example of /proc/interrupts from a dual-CPU system with an Adaptec dual-AIC7895 SCSI controller:

# cat /proc/interrupts
           CPU0       CPU1
  0:   98663989          0          XT-PIC  timer
  1:      34698      34858    IO-APIC-edge  keyboard
  2:          0          0          XT-PIC  cascade
  5:       7141       7908    IO-APIC-edge  MS Sound System
  6:          6          7    IO-APIC-edge  floppy
  8:   18098274   18140354    IO-APIC-edge  rtc
 10:    3234867    3237313   IO-APIC-level  aic7xxx, eth0
 11:         36         35   IO-APIC-level  aic7xxx
 12:     233140     216205    IO-APIC-edge  PS/2 Mouse
 13:          1          0          XT-PIC  fpu
 15:      44118      43935    IO-APIC-edge  ide1
NMI:          0
ERR:          0

In this example, you can see that interrupt 5 is used for the sound system, so it isn't available for a second parallel port. The two SCSI controllers are using interrupts 10 and 11, respectively, while the Ethernet controller shares interrupt 10. You may also notice that only one of the two standard IDE interfaces is enabled in the system BIOS, freeing interrupt 14 use for another device.

Here are the /proc/dma and /proc/ioports files from the same system:

# cat /proc/dma
0: MS Sound System
1: MS Sound System
2: floppy
4: cascade
# cat /proc/ioports
0000-001f : dma1
0020-003f : pic1
0040-005f : timer
0060-006f : keyboard
0070-007f : rtc
0080-008f : dma page reg
00a0-00bf : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : ide1
02f8-02ff : serial(auto)
0370-0371 : OPL3-SAx
0376-0376 : ide1
0388-0389 : mpu401
03c0-03df : vga+
03f0-03f5 : floppy
03f7-03f7 : floppy DIR
03f8-03ff : serial(auto)
0530-0533 : WSS config
0534-0537 : MS Sound System
e800-e8be : aic7xxx
ec00-ecbe : aic7xxx
ef00-ef3f : eth0
ffa0-ffa7 : ide0
ffa8-ffaf : ide1

On the Exam

You should be aware of the default resource assignments listed in Table 3-1. You should also know how to examine a running Linux system's resource assignments using the /proc filesystem.