The quad-core chips that have sat at the top of the microprocessor heap for two years are about to begin to be replaced by their bigger, burlier older brother - the 6-core processor.

Pat Gelsinger, senior vice president and general manager of Intel's Digital Enterprise Group, Wednesday afternoon announced that the company is set to release its 6-core Xeon processor for expandable servers in September. Dubbed Dunnington, the Xeon processor X7460 will be built with Intel's new 45-nanometer Penryn technology, the company said.

"The big cache and six cores will give customers a nice bump in performance," Gelsinger said previously. "We're quite excited about it."

Moving beyond quad-core processors, which to date have been the high-water mark in the semiconductor industry, is a major step - one that keeps Intel well ahead of rival Advanced Micro Devices, according to Dan Olds, principal analyst with the Gabriel Consulting Group.

"This is a big deal," said Olds. "It looks like, at least from the benchmarks we're seeing, that six-core chips offer more performance than quad-cores. So, yes, customers are going to want them. What we don't know is how much power the chips consume and how much heat they will dissipate, and those are key concerns. But, all in all, this is a pretty big advance in the state-of-the-art and all the major vendors are on board."

AMD, which has been getting its feet under itself after a rocky 2007, has shipped a lot of new products this year, including triple-core Phenom processors, along with quad-core Phenoms, graphics chips and chipsets.

But AMD hasn't yet launched its 45nm processor and it's not slated to release its upcoming 6-core Istanbul server processor until the second half of 2009 - about a year after Intel version ships.

"This will put a bunch of pressure on AMD," said Olds. "These chips outperform anything AMD has and probably win on price/performance too. This could cut AMD's share of the server market considerably."

And with Intel ahead of AMD in terms of market share, nanometer manufacturing and core-size, it's pressure that AMD could do without right now.

"Intel doesn't have to crank up chip performance right now to thwart AMD," added Olds. "Their current products handily outperform AMD on server products. From my own research, I can tell you that x86 server customers have moved away from AMD and towards Intel. So Intel didn't need to release this stuff now to catch up to AMD or to top them, but they're doing it anyway -- just to keep the pressure up on AMD and on themselves."

While it may be a shot at AMD, are customers eagerly waiting to buy 6-core machines? Maybe not, according to Jim McGregor, an analyst at In-Stat.

"If software can't take advantage of it, what does it buy you," said McGregor, noting that a lot of software today still isn't designed to take advantage of quad-core processing. "You still have software partitioning issues and when you put more cores on a chip, you have to run it slower or increase the power consumption budget or thermal limitations."

He added that if he had a choice, he would bypass the new 6-cores and hold out to buy 8-core machines. Intel's Nehalem, which is expected to go into production in the fourth quarter of this year, is designed to scale from two cores to eight cores.

Olds, however, said more server software than desktop applications are designed to take advantage of multi-cores.

Intel hasn't announced when it might release 6-core chips for the desktop and laptops.