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. |
