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Computerworld - Preliminary teardowns of Apple's iPhone 4S have confirmed what rumors claimed for months: The new smartphone is powered by the same dual-core processor used in the iPad 2.

Two teams -- one from iFixit, the other from IHS iSuppli -- have taken apart the new handset and published their results.

The iPhone 4S relies on the Apple-designed, dual-core A5 application processor, which is based on ARM's Cortex-A9 architecture, said iSuppli. That processor first made an appearance last March in Apple's iPad 2.

The A5 shows Apple is intent on continuing the practice it introduced last year, when it used the A4 processor -- the A5's predecessor -- first in the original iPad, then several months later in the iPhone 4.

Markings on the A5 strongly indicate that the iPhone 4S uses 512MB of system memory, iFixit and iSuppli said.

"How do we know it's 512MB? Check out the marking, specifically 'E4E4,' denoting two 2Gb LPDDR2 die -- for a total of 4Gb -- or 512MB," said iFixit in notes accompanying its teardown.

Talk had circulated earlier that the iPhone 4S might offer 1GB of system memory, double that of the iPhone 4 and the iPad 2.

iSuppli said that the 512MB showed Apple's confidence in its iOS mobile operating system.

"The use of this low density of memory highlights the efficiency of Apple's iOS operating system compared to those of competitive smartphones, which use twice as much SDRAM," said iSuppli in a statement attributed to senior analyst Wayne Lam. "This lowers the cost of this memory subsystem, leading to greater design economy relative to alternative phones."

Other mobile hardware experts added that sticking to 512MB of system memory also benefits the iPhone 4S' battery life.

"There are also potential battery life concerns with larger DRAMs: More room for apps to remain resident in memory leaves more DRAM cells to refresh, which impacts power consumption," said the website AnandTech today.

iFixit observed that the battery inside the iPhone 4S is rated at 5.3W-h (Watt-hour) capacity, slightly more than the 5.25W-h of the batteries used in both the AT&T and Verizon iPhone 4 models of 2010 and early 2011.

Also inside the iPhone 4S is a multi-network baseband processor -- the silicon that lets the smartphone make and take calls -- said iFixit and iSuppli.

"The iPhone 4S merges the HSPA and CDMA radio capabilities found separately in the two previous iPhone 4 models into a single product that can address global wireless networks, making it a world phone," said iSuppli. "No other handset OEM produces a single device for multiple operators and for multiple geographies on this scale."

During the unveiling of the iPhone 4S last week, Apple also touted the new handset as a "world phone" because the same model can be used on both GSM- and CDMA-based networks.

Lam of iSuppli had predicted the world phone last spring based on the appearance of a Qualcomm baseband processor in the Verizon iPhone 4.

At that time, Lam also said that the Verizon iPhone 4 pointed to a likely recycling of the internal design in the next model. "Apple should be able to retain about 95% of the design of the CDMA iPhone [in its next-generation device," said Lam in February.

Although Apple made multiple changes to the iPhone 4S -- among them replacing last year's 5-megapixel camera with an 8-megapixel camera -- according to iFixit, the similarities between the new phone and the iPhone 4 outnumber the differences.

The iPhone 4S went on sale today at Apple's retail stores other outlets in the U.S., the U.K, Australia, Canada, France, Germany and Japan. Although lines formed at some locations, supplies appeared to be sufficient to meet demand.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at  @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com.

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