To: BillyG who wrote (29978 ) 2/26/1998 9:29:00 PM From: BillyG Read Replies (1) | Respond to of 50808
Intel adds new instructions for multimedia processing. This article makes a big deal over the instructions, but the instructions don't seem too special. They appear to be similar to "software interrupt" instructions which quickly save the processor state for task switching. I would have been more concerned if Intel had instructions useful for MPEG-2 decoding........ Posted: 6:00 p.m. EST, 2/26/98 Intel to field performance-enhancing instructions in Deschutes By Alexander Wolfe SANTA CLARA, Calif. -- Intel Corp. has quietly added two new instructions to its Pentium II, in a bid to boost the processor's performance in complex applications including multimedia software. The instructions came to light in a Web posting by Clive Turvey, an independent software expert, who said he uncovered them while reading a recently released application note from Intel. "With the introduction of the Deschutes processor, Intel [has] added two new instructions: the FXSAVE and FXRSTOR instructions for a fast save and restore of the floating-point coprocessor's context," Turvey noted in his posting. Deschutes is the 333-MHz, 0.25-micron implementation of Pentium II that was unveiled in January. When word of the discovery hit the Web, it touched off immediate speculation-though not by Turvey himself-that details of Intel's second-generation "MMX2" multimedia extensions had been cracked. MMX2 are 70 new floating-point instructions intended to accelerate 3-D processing. They will appear in Intel's Katmai, an advanced 32-bit processor due next year. Intel's first generation of MMX instructions-introduced in Pentium-family CPUs in early 1997-consists of 57 op-codes, which speed multimedia applications by enabling programmers to process many chunks of data in parallel. However, Intel officials said the two new instructions have nothing to do with MMX. "FXSAVE and FXRSTOR are a fast save and a fast restore used for context switching in an operating system," said Jon Khazam, director of graphics at the Santa Clara chip maker. "They're intended to speed up the ability of the processor to switch threads." Specifically, the instructions cut the time required for context switching-the saving of processor-state information that's done when toggling between different software "threads." Reducing context-switching time is a way to improve operating-system performance. "These instructions are most definitely aimed at operating-system vendors and we anticipate that they'll be used in new OSes," Khazam said. Indeed, it's expected the instructions will be exploited by Windows 98 and Windows NT 5.0, two upcoming offerings from Microsoft Corp. Context switching is also crucial to the performance of software that uses the MMX multimedia instruction-set extensions. That's because MMX apps must frequently toggle between MMX op-codes and floating-point instructions. But while Intel is moving to the second generation of MMX in Katmai, it plans to use a different name for the 70 new instructions. "We're not calling them MMX2," said Khazam. "We're calling them 'Katmai new instructions,' or 'Katmai NI.' " However, Intel will maintain the existing MMX name for its 57 original instruction-set extensions. "MMX instructions are distinct from Katmai NI," said Khazam. The original MMX instructions are "part of the permanent Intel architecture and will always be there." Khazam also insisted that Intel isn't secretive about its new-instruction plans. "These instructions are going to be fully documented when we do the main Deschutes launch in April," he said.