VoIP Voice and Fax Signal Processing

19.4 OPERATING SYSTEM ASPECTS ON DIFFERENT PLATFORMS

In this section, VoIP-specific operating system aspects are considered for the following combinations:

1. Computer-based VoIP
2. DSP-and network-processor-based architectures
3. Network processor with built-in DSP instruction extensions
4. DSP with network extensions

In the following sections, the keywords “MIPS”, “mips”, “MCPS”, and “MHz” are used. To convey clarity in information, the following clarifications are provided for these keywords.

19.4.1 Keywords MHz, MCPS, MIPS, and DMIPS Association

Several terms are used to describe processor performance. This section deals with the description of those terms. Processors typically have a master clock signal that times the execution of instructions. The frequency of this clock signal is normally measured in MHz, where 1 MHz represents a clock frequency of one million (1,000,000) cycles per second. The term “MCPS” may be used interchangeably with “MHz”, but it is less common.

Modern processors used in VoIP systems typically execute one instruction per clock cycle; however, some processors require more than one clock to execute each instruction (older processors and some DSPs), and others can execute more than one instruction per clock (superscalar architectures). Thus, it is necessary to have some approach to measure processor performance independent of this clock speed. One common approach is to state the number of instructions executed per second, which is often called million instructions ...