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Computerworld - Apple Inc.'s iPad is about twice as fast as the current iPhone, according to recently-published benchmark tests.

The results fit the assumption that the iPad is powered by a single-core ARM processor, an Apple product repair expert said today.

On average, the iPad executes native applications about twice as fast as does the iPhone 3GS, said Craig Hockenberry, who works for Iconfactory, best known as the developer of Twitterific, a Twitter client. Iconfactory released an iPad version of Twitterific last week.

After comparing the performance of iPad and iPhone native applications, as well as the two devices' JavaScript execution speeds, Hockenberry posted results on his personal blog last Saturday.

Hockenberry measured the speed that the iPad and iPhone 3GS each ran an application written with Apple's Cocoa Touch API using the company's SDK (software developers tool kit). The two devices rely on different versions of Apple's iPhone operating system, however; the iPad runs iPhone 3.2, while the iPhone 3GS uses 3.0.

The iPad's JavaScript performance increases were less impressive, said Hockenberry. "The same 2x improvement is not seen for the same benchmarks when executing JavaScript code in Web pages," he said. "Things have definitely improved [in the iPad], but there was a wide variation in results when performing the tests. I suspect that just-in-time compilation or other similar types of caching are affecting the results."

Just-in-time compilation, or JIT, is a technique that improves runtime performance by compiling JavaScript into native code just before executing, rather than letting the JavaScript run through an interpreter. Apple added a new JIT compiler to Safari's JavaScript engine with Version 4.0 of the browser, which launched last summer.

Hockenberry's results for the iPad are consistent with the performance boost one would expect from a single-core ARM processor running at 1 GHz, said Aaron Vronko, CEO of Portage, Mich.-based Rapid Repair. Vronko, whose company repairs and supplies parts for Apple's iPod, iPhone and iPad, disassembled an iPad last weekend to get a better idea of what was inside.

"This performance increase over the iPhone 3GS is exactly in line with what I've expected, based on a single-core ARM Cortex-A9 CPU running at 1 GHz," Vronko said today. Last January, Vronko said he would expect the iPad to run software 85%-to-90% faster than the iPhone 3GS.

Vronko explained that the iPad's processor -- which like the iPhone's is actually integrated within a system-on-a-chip, or SOC -- is 67% faster in clock speed than the iPhone 3GS's ARM Cortex-A8 CPU running at 600 MHz. "So in terms of speed increases, this new CPU sees both a 67% faster clock rate, in addition to being able to complete more operations per clock cycle thanks to innovations in ARM's latest CPU design," said Vronko, citing such factors as native support for an expanded processor instruction set and a shorter code execution pipeline.