Apple launches liquid-cooled G5 Mac

Power Mac family goes fully dual-processor

Apple today updated its Power Mac G5 desktop line, equipping each machine with two processors, as expected, including a top-end model clocked to 2.5GHz.

What was not anticipated, however, is the introduction of liquid cooling technology, which potentially calls into question the energy efficiency of the G5 processor at high clock frequencies. The liquid system - "more efficient than a traditional heat sink", says Apple - is only used in the 2.5GHz model.

Apple has been known to be exploring liquid cooling technology for some time. Last October it emerged that the company had been working on prototype systems with US-based start-up Cooligy, which has developed a scheme for directly cooling a CPU with water.

Cooligy's approach - called Active Micro-Channel Cooling (AMC) - involves scoring hundreds of tiny channels into a silicon layer placed on the upper surface of the chip package. Water circulates through the channels drawing heat away from the core. Cooligy claims AMC can cool a CPU by up to 1kW per square cm. The best a passive system can manage, it says, is 250W per square cm.

However, Cooligy tells us that it is not supplying the fluid cooling system for the G5

The new Apple line-up comprises three models, with dual 1.8GHz, 2GHz and 2.5GHz 64-bit processors, respectively, with 900MHz, 1GHz and 1.25GHz frontside bus speeds per CPU. The low-end model supports up to 4GB of 400MHz DDR SDRAM and ships with 256MB. The other two Macs can handle up to 8GB of memory, but ship with 512MB apiece. Both come with 160GB Serial ATA hard drives; the 1.8GHz model has an 80GB unit.

The bottom two models bundle an Nvidia GeForce FX 5200 Ultra graphics card with 64MB of DDR video RAM. The 2.5GHz model has an ATI Radeon 9600 XT with 128MB of VRAM. All three models ship with a 8x DVD-R/CD-RW 'superdrive'.

Available now, the 1.8GHz and 2GHz machines cost £1499/$1999 and £1849/$2499, respectively. The £2199/$2999 2.5GHz dualie will ship in July. UK prices include VAT. ®

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