System information
Linux has historically had problems with its ability to service IRQs
quickly; this problem has caused enough trouble for audio devel-
opers that several patches have been created to address this short-
coming. So far, there has been some mild controversy over how to
incorporate these patches into the Linux kernel.
Kernel version
Asterisk is officially supported on Linux version 2.6. Almost all of Asterisk itself
does not really care about the kernel version, but DAHDI requires 2.6.
Linux distribution
Linux distributions are many and varied. Asterisk should work on all of them.
Choose the one that you are most comfortable with.
Choosing a Processor
Since the performance demands of Asterisk will generally involve a large number of
math calculations, it is essential that you select a processor with a powerful FPU. The
signal processing that Asterisk performs can quickly demand a staggering quantity of
complex mathematical computations from the CPU. The efficiency with which these
tasks are carried out will be determined by the power of the FPU within the processor.
Actually naming a best processor for Asterisk in this book would fly in the face of
Moore’s Law. Even in the time between the authoring and publishing of this book,
processor speeds will undergo rapid improvements, as will Asterisk’s support for var-
ious architectures. Obviously, this is a good thing, but it also makes the giving of advice
on the topic a thankless task. Naturally, the more powerful the FPU is, the more
concurrent DSP tasks Asterisk will be able to handle, so that is the ultimate consider-
ation. When you are selecting a processor, the raw clock speed is only part of the
equation. How well it handles floating-point operations will be a key differentiator, as
DSP operations in Asterisk will place a large demand on that process.
Both Intel and AMD CPUs have powerful FPUs. Current-generation chips from either
of those manufacturers can be expected to perform well.
‡
The obvious conclusion is that you should get the most powerful CPU your budget will
allow. However, don’t be too quick to buy the most expensive CPU out there. You’ll
need to keep the requirements of your system in mind; after all, a Formula 1 Ferrari is
ill-suited to the rigors of rush-hour traffic. Slower CPUs will often run cooler, so you
might be able to build a lower-powered, fanless Asterisk system for a small office, which
could work well in a dusty environment, for example.
‡ If you want to be completely up-to-the-minute on which CPUs are leading the performance race, surf on over
to Tom’s Hardware (http://www.tomshardware.com) or AnandTech (http://www.anandtech.com), where you
will find a wealth of information about both current and out-of-date CPUs, motherboards, and chipsets.
644 | Appendix C: Preparing a System for Asterisk