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Velocity Engine

The Velocity Engine, embodied in the G4 and G5 processors, expands the current PowerPC architecture through addition of a 128-bit vector execution unit that operates concurrently with existing integer and floating-point units. This provides for highly parallel operations, allowing for simultaneous execution of up to 16 operations in a single clock cycle. This new approach expands the processor's capabilities to concurrently address high-bandwidth data processing (such as streaming video) and the algorithmic intensive computations which today are handled off-chip by other devices, such as graphics, audio, and modem functions.The AltiVec instruction set allows operation on multiple bits within the 128-bit wide registers. This combination of new instructions, operation in parallel on multiple bits, and wider registers, provide speed enhancements of up to 30x on operations that are common in media processing.

Technical Resources
Optimizing for the Power Mac G5
The full capabilities of the Power Mac G5 are available to those who optimize their applications for the new system. Learn how to analyze your code and reap the full benefits of the G5 for both new and existing apps.
Quick Start Guide for AltiVec
This overview web page should help those new to AltiVec get started quickly.
Apple/Genentech BLAST Performance Data (PDF)
This document shows the performance of A/G BLAST relative to NCBI BLAST distribution code running on a 2 GHz Pentium 4 system.
Are you accelerated for G4?
The "Accelerated for G4 with Velocity Engine" promotional graphic was designed to enable easy identification of software products that have been optimized to take advantage of performance increases available from the G4 processor. The graphic can be used as a sticker on qualifying software packages, in advertising and marketing communications, and as a badge on web sites to promote the inclusion of Altivec technology instructions that enable increased performance for qualifying software products. Please see Apple's Hot News for more information.
Contact Us
Send comments and questions about the G4 to Apple's AltiVec email address,
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