Книга: Fedora™ Unleashed, 2008 edition

Preparing for Potential Hardware Problems

Preparing for Potential Hardware Problems

Fedora will work "out of the box" with nearly every Intel-or PowerPC-based desktop, server, and laptop; drivers for thousands of different types of hardware peripherals are included. But you can sometimes run into problems if Linux does not recognize a hard ware item, if Fedora does not correctly initialize the hardware, or if an initialized item is incorrectly configured. For these reasons, some hardware items are prone to creating problems during an install. In the sections that follow, you learn some important pointers for avoiding these problems or resolving those that do occur.

Controllerless Modems

As you read earlier, most Linux hardware-related installation problems stem from a lack of technical specifications from the manufacturer, thwarting efforts of open source developers to create a driver. In the recent past, one hardware item that triggered both types of difficulties was the controllerless modem, also colloquially known as a WinModem. The good news is that modem chipset manufacturers have been more forthcoming with driver details. Some original equipment manufacturers, such as IBM, have made a concerted effort to provide Linux support. Support for the ACP Mwave modem, used in ThinkPad 600/Es and 770s, is included in the Linux kernel. Drivers have been developed for many of the controllerless modem chipsets that formally did not work with Linux.

If a driver is not available for your controllerless modem, you have a few options. You can download the driver's source code and build the driver yourself. Alternatively, you can download a binary-only software package and install the driver.

Some controllerless modems might also need to be initialized and configured through a separate utility program. The modem, if supported, should work normally after you install and configure the driver.

You can research Linux support for controllerless modems by browsing to http://www.linmodems.org/.

USB Devices

Fedora supports hundreds of different Universal Serial Bus devices. USB is a design specification and a protocol used to enable a host computer to talk to attached peripherals. Because of lack of manufacturer and device ID information or lack of technical specifications regarding certain chipsets, some devices might not work with Fedora. USB 1.1 devices are designed to support data transfer speeds between 1.5 and 12Mbps.

Common USB devices include cameras, keyboards, mice, modems, network interfaces, printers, scanners, storage devices, video (such as webcams), and hubs (to chain additional devices).

Although most enlightened manufacturers are aware of opportunities in the Linux marketplace, some still do not support Linux. It pays to determine Linux support before you buy any USB device; again, research Linux USB support and its current state of development by browsing tohttp://www.qbik.ch/usb/devices/.

The newer USB 2.0 specification enables devices (such as hard and CD drives) to use speeds up to 480Mbps. Fedora supports USB 2.0 with the ehci-hcd kernel module. This driver, in development since early 2001, enables the use of many forms of newer USB 2.0 devices as long as you have a supported USB controller. Check out the current state of Linux USB 2.0 support by browsing tohttp://www.linux-usb.org/usb2.html.

Motherboard-Based Hardware

Small form factor PCs, thin clients, notebooks, and embedded devices are part of a growing trend in the PC industry. Manufacturers are cramming more functionality into fewer chips to simplify design and lower power requirements. Today, many computers come with built-in video graphics, audio chipsets, and network interfaces, along with a host of peripheral support.

Common modern (1996 onward) PC motherboard form factors are designed according to industry-assigned specifications (usually from Intel), and are ATX (12-9.6 inches); MicroATX (9.6-9.6 inches); and FlexATX (9-7.5 inches). One of the newest and even smaller motherboard forms is from VIA Technologies, Inc. — the mini-ITX (approximately 6.5-6.5 inches), which has an embedded CPU. CPUs commonly used in all these motherboards will vary, and have different socketing requirements based on chipset pins: Socket 478 for K7-type CPUs (from AMD); Socket 939 for some Athlon and Sempron processors; Socket AM2 for newer Athlon 64 and AMD FX processors; Socket 370 for Pentium IIIs and Celerons from Intel, or C3s from VIA; Socket 478 for Intel's Pentium 4s (early versions of which used a 423-pin socket); and Socket LGA775 for newer Core 2 and Pentium D processors. Older socket types are Socket A, Socket 7 (and Super 7), Slot 1, and Slot B.

Fortunately, nearly all controllers, bridges, and other chipsets are supported by Linux. Although flaky or unsupported built-in hardware can (usually) be sidestepped by the installation of a comparable PCI card component, cutting-edge notebook users are at the most risk for compatibility problems because internal components are not user replace able. Potential pitfalls can be avoided through careful research (vote with your money for Linux-compatible hardware), or by choosing PC motherboards with a minimum of built- in features, and then using PCI (Peripheral Component Interconnect), AGP (Accelerated Graphics Port), or PCI Express cards known to work.

CPU, Symmetric Multiprocessing, and Memory Problems

Fedora supports all Pentium class x86 compatible CPUs. Code is included in the Linux kernel to recognize the CPU type when booting, and to then implement any required fixes to overcome architecture bugs (such as the now-infamous divide-by-zero error). After you install Fedora, you can also rebuild the Linux kernel to specifically support and take advantage of the host PC's CPU. You might not realize extreme improvements in computational speed, but you'll be assured that Linux is crafted for your CPU's architecture, which can help stability and reliability. Some of the x86-based CPUs with specific supporting code for Linux include those from Advanced Micro Devices, Transmeta, and VIA Technologies.

Fedora's Linux kernel also should automatically recognize and use the amount of installed RAM. The Linux kernel should also recognize and map out any memory holes in system memory (perhaps used for video graphics).

If you are installing Fedora on a working, stable PC, you should not have any problems related to the system's memory. If you are putting together a new system, you need to avoid combining or configuring the system in ways that will interfere with its capability to process data. Some issues to be aware of include the following:

? Do not expect similar CPU performance across product lines from different manufacturers, such as AMD or VIA. Some CPU models offer better floating point or integer math operations, which are important for a number of CPU-intensive tasks (such as graphics, audio, and video rendering or conversion). If you need better performance, try to find a faster CPU compatible with your motherboard, or switch to a CPU with better floating-point unit (FPU) performance.

? Overclocking can cause problems with overheating, memory access, and other hardware performance, and it is not a good idea for any Linux system. Overclocking is a popular geek pastime and a great way to get a bit of performance boost out of slower CPUs by altering voltage settings and/or clock timings via the BIOS. You can try to push your CPU to higher speeds, but this approach is not recommended if your aim is system stability. The Linux kernel reports the recognized CPU speed on booting (which you can view by using the dmesg command).

? Along the same lines, CPU and motherboard overheating will cause problems. Proper attachment of the CPU's heatsink using a quality thermal paste (never use thermal tape), along with one or more fans providing adequate airflow lessens the chance of hardware damage and system failure.

? You can run into problems if you switch the type of CPU installed in your computer, and especially if your PC's BIOS does not automatically recognize or configure for newly installed mainboard hardware and components. In some instances, a system reinstall is warranted, but BIOS issues should be resolved first.

? Not all CPUs support symmetric multiprocessing, or SMP. Fedora readily supports use of two or more CPUs and, during installation, automatically installs an appropriate Linux kernel. You can avoid problems by reading the Linux SMP HOWTO (available through http://www.tldp.org/). Note that some CPUs, such as the current crop of VIA C3s, might not be used for SMP. Also, SMP motherboards require that all CPUs be identical. This means that you need two identical CPUs to take advantage of SMP.

? Faulty or bad memory causes Linux kernel panics or Signal 11 errors (segmentation faults), causing a system crash or a program to abort execution. Linux is quite sensitive to faulty hardware, but runs with great stability in a correctly configured system with good hardware. Problems can arise from incorrect BIOS settings, especially if video memory must occupy and use a portion of system RAM. Always install quality (and appropriate) memory in your PC to avoid problems.

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