<?xml version="1.0" encoding="UTF-8"?> <!-- Copyright (c) 2017 OpenPOWER Foundation Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <section xmlns="http://docbook.org/ns/docbook" xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="sec_differences"> <title>Profound differences</title> <para>We have already mentioned above a number of architectural differences that affect porting of codes containing Intel intrinsics to POWER. The fact that Intel supports multiple vector extensions with different vector widths (64, 128, 256, and 512 bits) while the PowerISA only supports vectors of 128 bits is one issue. Another is the difference in how the respective ISAs support scalars in vector registers. In the text above we propose workable alternatives for the PowerPC port. There are also differences in the handling of floating point exceptions and rounding modes that may impact the application's performance or behavior.</para> <xi:include href="sec_floatingpoint_exceptions.xml"/> <xi:include href="sec_floatingpoint_rounding.xml"/> <xi:include href="sec_performance.xml"/> </section>