The next Itanium chip will no longer include a feature that Intel once banked on, but that never proved successful.
Circuitry to let Itanium run software for x86 chips, such as Pentium and Xeon chips, is not present in the forthcoming "Montecito" processor, according to the 176-page reference manual for the chip published this week (click here for PDF).
Instead, anyone wishing to run programs for x86 chips on Montecito must use Intel emulation software called IA-32 Execution Layer, or IA-32 EL, that was first released in 2004.
"IA-32 EL provides much better performance and flexibility for 32-bit applications on Itanium," spokeswoman Erica Fields said of the choice. "With Montecito, we took back the silicon area that was being used up by the x86 hardware support."
The change, which Intel had refused to discuss until now, reflects the company's diminished Itanium ambitions, which cast the chip as being only for higher-end servers. Intel's retreat to that market segment was in part because Itanium couldn't run x86 software effectively, which imposed major transition burdens on software companies and server customers.
Itanium's delays and poor initial performance meant that the x86 support wasn't useful when it arrived. The chip also lacked support for newer x86 features. "Basically, no one ever used hardware-based IA-32 execution, so better to use the silicon for something else," said Illuminata analyst Gordon Haff. "Of course, basically no one uses software-based emulation either, but at least that doesn't cost chip real estate."
Support for IA-32 EL is necessary for operating systems on Montecito, according to the manual. "All OSes running on Montecito have a requirement to have IA-32 EL installed," the manual said.
Microsoft Windows and major Linux versions include IA-32 EL. The emulation layer is considerably slower than a modern Xeon however: A 1.5GHz Itanium 2 processor runs emulated x86 instructions at about the same speed as a 1.5GHz Xeon processor, according to Intel.
When Intel and Hewlett-Packard announced the collaboration to build what became the Itanium processor family in 1994, they promised the chips would be able to run software written for the two lines they were intended to replace, Intel's x86 chip and HP's PA-RISC.
"The planned architecture will maintain binary compatibility with both companies' software bases," the companies said in the 1994 press release. Support for PA-RISC software came through an emulation technology called Aries, but Intel had hoped for faster x86 support by including direct hardware support on Itanium chips.
Reworking software for Itanium isn't an onerous problem, especially for major software companies, but there's more to porting software than the initial technical work, Haff said. "The issue is providing service and support for a unique binary, not the port," he said.
Itanium once had the support of all the top server makers. But Sun Microsystems--never a major Intel ally--, and and dropped their Itanium server products in 2005.
Intel's most recent Itanium problem cropped up last October, when the chipmaker .
HP, which dominated the Itanium server market with 79 percent of all shipments in the third quarter of 2005, is working with Intel and others to improve Itanium's software availability.
A year ago, software, hardware and marketing work. And more recently, HP and Intel joined lesser Itanium allies to launch the Itanium Solutions Alliance to improve software support.
The alliance is still active. Members plan to announce a new funding initiative Jan. 26 in San Francisco.