Eight months ago Intel rocked the mobile processor world with its first dual-core CPUs, which boosted the speed of a notebook performing two tasks simultaneously by 30 per cent. Now comes Core Duo's successor, Core 2 Duo, accompanied by Intel claims of even better performance and support for the coming era of 64-bit computing. Should you kick yourself for buying that Core Duo notebook in May?

PC World (Digit's sister magazine) tests suggest you shouldn't sweat it too much. Notebooks get only a small performance boost with Intel's new processor, formerly code-named Merom, and battery life appears to remain about the same.

The five new Core 2 Duo mobile chips (Intel earlier released five Core 2 Duo desktop processors) are the latest descendants of Intel's Centrino-brand processor and wireless chip set combo.

Core 2 Duo comes in two lines: the T5000, which includes the 1.66GHz T5500 and 1.83GHz T5600, and the T7000, featuring the 2GHz T7200, the 2.16GHz T7400, and the 2.33GHz T7600. Intel isn't saying when we'll see a version of the Core 2 Duo for ultraportables.

Core Duo vs Core 2

The Core 2 Duo chip has many of the same features as its Core Duo predecessor: a 667MHz frontside bus, the 945 chip set, the 3945ABG wireless chip set, and similar clock speeds. The two biggest improvements are the doubling of Level 2 cache to 4MB in the T7000 line, and support for 64-bit processing. The latter brings Intel back on par with AMD's Turion 64 X2 chip and means users can take advantage of upcoming 64-bit applications, including the 64-bit version of Windows Vista. Core Duo can't do 64-bit computing.

Core Duo 2 notes for all purposes

PC World tested three shipping notebooks with different Core 2 Duo processors and 1GB of memory: a $1,906 Dell M1210 with a 2GHz T7200 chip, a $2,059 Gateway M685-E with a 2.16GHz T7400 chip, and a $1,498.99 HP Pavilion dv6000t with a 1.83GHz T5600 chip.

The biggest performance increase over notebooks outfitted with same-speed Core Duo CPUs was only 7 per cent, enough to shave a few seconds off of day-to-day operations but not much more.

The Windows XP Media Center Edition-equipped Dell M1210 turned in a WorldBench 5 score of 102, 5 per cent better than the 97 earned by the average Media Center Edition notebook using a 2GHz Core Duo T2500. The Gateway M685-E scored 109, 7 per cent better than the 2.16GHz Core Duo T2600-equipped HP Compaq nx9420's score of 101. The HP Pavilion dv6000t scored 101, 6 per cent better than a 1.83GHz Core Duo T2400-equipped Toshiba Satellite P105-S921's 95 with the same 2MB of Level 2 cache.

In sum, Core 2 Duo systems are a tad faster than Core Duo notebooks at handling everything from mainstream applications such as spreadsheets and email to watching DVD movies. And they are just as impressive (and significantly faster than Pentium-Ms) at juggling multiple tasks, like ripping a CD while surfing the Net, for instance.

Battery life a washout

Core 2 doesn't appear to significantly affect battery life. The Dell M1210, a 12.1-inch multimedia wide-screen model, lasted the longest: 4 hours and 23 minutes with its 9-cell battery upgrade. The Gateway M685-E, a bulky 17-inch wide-screen, lasted 3 hours and 41 minutes thanks to a 12-cell battery upgrade. That's better than the 2.3 hours we got with a 2GHz Core Duo T2500 version of the M685-E tested earlier this year, but the older unit had a less powerful 8-cell battery upgrade.

The HP Pavilion dv6000t, a 15.4-inch multimedia wide-screen unit and the only one in the group equipped with a standard six-cell battery, ran out of juice after only 2 hours and 10 minutes. An HP Pavilion dv2000t equipped with a 2.16GHz Core Duo T2600 that we also tested this month lasted over 7 hours -- but that notebook had a 14.1-inch wide-screen display and its battery was twice as strong as the dv6000t's.

Intel is pricing the Core 2 Duo the same as Core Duo chips, which means the new processors won't drive up overall notebook prices.

Get a deal on older duos

In fact, shoppers can soon expect a fire sale on Core Duo notebooks, said Samir Bhavnani, director of research for Current Analysis in San Diego. "It's going to be hard for people to tell the difference between retail Core Duo and Core 2 Duo because the names and the processor speeds look so alike, so you're going to see Intel get very aggressive with Core Duo pricing."

Given also that Core 2 Duo's support for 64-bit applications won't be important for at least another year, consumers should think long and hard about paying a premium to get a Core 2 notebook instead of a Core Duo. "Buying a 64-bit capable Core 2 Duo notebook right now is like buying a Playstation 3 when there won't be any games for another two years," Bhavnani said.