Pentium III extended floating point support
UnixWare 7 Release 7.1.1 contains enhancements that provide extended floating
point and other operations for processors that support them.
Since the introduction of the first Pentium chips, Intel has enhanced
the instruction set for their Pentium II 350-450, Pentium
II/Xeon, and Pentium III processors.
Release 7.1.1 provides support for:
extended floating point save and restore instructions (fxsave
the Streaming SIMD
(Single Instruction Multiple Data) instruction set
47 MMX instructions added for the Pentium II processor and P-II
83 instruction mnemonics added for the Pentium III, which includes 12
additional MMX instructions and 8 cacheability control instructions
These enhancements were originally released to customers as ptf7406,
The benefits of this support are:
to enable the kernel to take advantage of the faster saving and
restoring of floating point state provided by the fxsave
and fxrstor instructions
to allow applications to use the Streaming SIMD
instructions and the Pentium III extended floating point registers
to enable developer tools like as, dis, fur,
kdb, scodb, crash, and debug
to handle the new instructions and MMX registers
Systems with CPUs that do not support the new
instructions will perform as in previous releases.
Applications can be written using the new function calls provided for
extended floating point support, and can test to see if the processor
supports extended floating point instructions.
Documentation for the Intel Pentium instruction set
is available from the vendor, and is not shipped with
Summary of changes
The following list summarizes the changes made for Release 7.1.1 to
support the Pentium III instruction set:
Exceptions to extended floating point support
The following exceptions apply to extended floating point instruction
support in Release 7.1.1:
The C compiler and optimizer have not been enhanced to generate and optimize
Pentium III Streaming SIMD or other new instruction.
While source files containing the new instructions can be processed by
and the resulting object files used as input to
only the linking phase of cc applies to such files.
Unmasked extended Pentium III floating point exceptions are not supported.
Applications generating unmasked extended floating point
exceptions will terminate when the exception is generated.
Release 7.1.1 does not include changes to the threads library
(libthread) to support extended floating point state.
For applications that use threads (see
the contents of the extended floating point registers will be
undefined when used by multiple threads.
If threaded applications use the Pentium III extended floating point
registers, the results will be unpredictable.
New user context structure and floating point context flag
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 22 April 2004