Today's fixed-point processors are entering a performance realm where they can satisfy some floating-point needs without requiring a floating-point processor. Choosing among floating-point and extended-precision fixed-point allows designers to balance dynamic range and precision on an as-needed basis, thus giving them a new level of control over DSP system implementations.
In general, the cutting-edge fixed-point families tend to be fast, low power, and low cost, while floating-point processors offer high precision and wide dynamic range.
* Floating-point processor performance can be measured in Specmarks published by Spec International.
In addition to handling fixed-point arithmetic, the integer processor performs data address computations for both itself and the floating-point processor. Precisely when data are to be moved between the processors and the data cache is determined by the integer unit.
Underneath these aptly-named machines is the POWER (Performance Optimization With Enhanced RISC) architecture and power is what it delivers: RISC-based CPUs, up to four instructions per cycle, and an integrated floating-point processor
that bests Sun's 4/330 performance by a factor of five according to Texas A&M university tests.
do have some advantages over fixed-point processors:
Many of the digital examples provided in Figure 2 are floating-point processors
with typically 32-bit or higher precision arithmetic whose accuracy and dynamic range exceed the analog-device capabilities but at a much lower processor bandwidth.