Apple will use the AltiVec instruction set in Macintosh computers and expects to have AltiVec-enabled Macs for sale in the first half of next year, the company said at its Worldwide Developers Conference Tuesday.Apple officials made it clear that AltiVec is a big part of the Mac's future -- the Mac OS is even being altered to exploit the instructions.
Speaking at the conference's hardware keynote, senior vice president of hardware engineering Jon Rubinstein said Apple had spent two years assisting Motorola in developing AltiVec, which consists of 162 new PowerPC instructions that target multimedia applications and are optimized for Mac OS native code.
"This is not some tacky little add-on to the chip," said Keith Diefendorff, director of processing architecture for Apple, and the company's chief AltiVec architect. "This is a significant investment in transistors."
Initially dubbed "VMX," for "vector multimedia extension," AltiVec adds an independent vector unit, aside from the integer and floating-point units within a chip, to provide a faster and wider path for multimedia-driven calculations. The vector unit has 32 registers of 128 bits each, and a dedicated 128-bit pipeline to memory, which is wider than the 64 bits available to the floating-point unit.
Apple hopes AltiVec goes beyond its multimedia roots and provides a speed boost to any algorithm that can take advantage of parallel processing. Apple has already tried this with several algorithms, and Diefendorff encouraged developers to do the same.
"The real speed-up will be from people who go into their algorithms and rewrite them with vector [operations] in mind," he said. Apple will do some fine-tuning, and plans to tweak its Mac OS and QuickTime Media Artchitecture to better exploit AltiVec, he said.