The VFP9-S coprocessor provides full IEEE 754 standard
compatibility through a combination of hardware and software. There
are rare cases that require significant additional compute time
to resolve correctly according to the requirements of the IEEE 754
standard. For instance, the VFP9-S coprocessor does not process
subnormal input values directly. To provide correct handling of
subnormal inputs according to the IEEE 754 standard, a trap is made
to support code to process the operation. Using the support code
for processing this operation can require hundreds of cycles. In
some applications this is unavoidable, because compliance with the
IEEE 754 standard is essential to proper operation of the program.
In many other applications, especially in the embedded market, strict
compliance to the IEEE 754 standard is unnecessary, while determinable
runtime, low interrupt latency, and low power are of more importance. The
following sections describe the two VFP9-S coprocessor modes
of operation: