Apple has announced three new dual-processor Power Mac G5 configurations, with the fastest model topping out at 2.5GHz.

The new high-end systems miss the 3GHz mark that Apple CEO Steve Jobs said the company would achieve at last year's Worldwide Developers Conference, but Tom Boger, Apple's Director of Power Mac Product Marketing said it came down to a technology challenge that was bigger than they expected.

Boger also said that users shouldn't expect to see a PowerBook G5 before the end of the year because of the challenges of putting the G5 in a small enclosure. Anyone that has seen the heatsink from a Power Mac G5 knows that it would not fit in a portable computer. This is the challenge that faces Apple as it tries to move its pro product line to the new fast processor technology.

"I think it's important to realise that the technical challenges are not trivial putting that G5 in a PowerBook or anything else and not to expect a G5 anytime soon in a PowerBook - certainly not before the end of the year," said Boger.While Boger didn't give a timeframe for an iMac G5, he did say the company faced similar challenges getting a G5 to work with their consumer desktop.

"It's the same story - the challenges are obvious when you look at the G5 and the size of the heatsinks and the enclosure; that would be a heck of a challenge as well."

When Jobs took the stage at last year's Worldwide Developer's Conference, he wowed the attendees with the new Power Mac G5 dual 2GHz design and technology. He further excited the crowd when he said that Apple would release a 3GHz model within a year - with two weeks to go before that deadline, Boger said Apple will not meet the 3GHz promise.

"It's actually quite simple," said Boger. "When we made that prediction, we just didn't realise the challenges moving to 90-nanometer would present. It turned out to be a much bigger challenge than anyone expected. All-in-all, no, we are not getting to 3GHz anytime soon, but what we are announcing today is a very significant upgrade in performance and its something that are customers will be very happy with."

All systems share some common traits: an 8x speed DVD-R/CD-RW "SuperDrive", a single Firewire 800 port, two FireWire 400 ports (one in the back, one in front), three USB 2.0 ports (two in the back, one in front), Gigabit Ethernet and 56K modem, AGP 8x Pro graphics card slot, ADC and DVI video interfaces. They're ready for AirPort Extreme wireless networking cards and can be ordered with internal Bluetooth support as well. Analog and optical digital audio inputs and outputs are supported as well.

The low-end Power Mac G5 sports dual 1.8GHz processors and a frontside bus clocked at 900MHz per processor. The system comes equipped with 256MB of DDR SDRAM memory expandable to 4GB, and an 80GB Serial ATA hard drive. It ships with an Nvidia GeForceFX 5200 Ultra graphics card, equipped with 64MB of memory, and it's also equipped with three full-length 33MHz 64-it PCI slots for further expansion. It costs US$1,999 - $200 more than the previous low-end model, which features a single processor configuration.

The mid-range model ships with dual 2.0GHz processors and a 1GHz frontside bus. It ships with 512MB of DDR SDRAM memory, expandable to 8GB, and a 160GB Serial ATA hard drive. The system also ships with a GeForce FX 5200 Ultra graphics card, and features three 64-bit PCI-X expansion slots (one clocked at 133MHz, the other two at 100MHz). It costs $2,499.

The forthcoming high-end model will feature dual 2.5GHz processors operating on 1.25GHz frontside buses, 512MB DDR SDRAM, and a 160GB Serial ATA hard drive. Like its mid-range sibling, the top model will feature three PCI-X slots, one at 133MHz and two at 100MHz. It uses an ATI Radeon 9600 XT graphics card with 128MB of memory. The 2.5GHz system also features a liquid cooling system that Apple says helps reduce temperature without increasing fan noise. The 2.5GHz model will cost $2,999 when it's released in July.

"The top of the line model uses a new cooling system - it's a state-of-the-art liquid cooling system that's only available on the high-end model. It's a closed loop system and basically liquid runs by each processor, pulling heat away from the processor and it's returned back to a grill that fans are blowing air over, returning the liquid to its original temperature. It's completely maintenance free and is very quiet, which is important for this product line," said Boger.

All systems come equipped with Mac OS X v10.3 and a suite of software. The new 1.8 and 2.0GHz models are available now and Apple expects the 2.5GHz model to ship in July.

In announcing the new Power Mac G5 models, Apple also indicated that its single-processor Power Mac G4 models have been taken out of production. Since the Power Mac G5's introduction Apple has continued to manufacture and offer 1.25GHz Power Mac G4 systems in single and dual-processor versions. Apple said the $1,299 Power Mac G4 "will no longer be in production and is available for purchase while supplies last."