iPhone 4S’s underclocked A5 chip smokes iPhone 4, graphics performance 21 percent slower t han iPad 2

9 to 5 Mac
Christian Zibreg

First SunSpider and BrowserMark benchmarks 9to5Mac told you about yesterday confirmed the iPhone 4S as being “twice as fast” per Apple’s tagline. Today, AnandTech published a more thorough analysis stemming from Javascript, CPU and GPU benchmarks of Apple’s latest handset. Thanks to the dual-core A5 chip that first debuted in the iPad 2 this Spring, Javascript performance on the iPhone 4S “finally catches up to Tegra 2 based Honeycomb devices, while general CPU performance is significantly higher than the iPhone 4″.

More importantly, Geekbench results (seen below) tell us the iPad 2 is clocked around “25 percent higher than the iPhone 4S”. Overall, the Apple-designed dual-core A5 chip inside iPhone 4S is estimated to run at 800MHz versus iPad 2′s 1GHz A5 processor. This isn’t entirely unexpected due to the battery concerns and the handset’s much smaller 5.25 Whr battery. Furthermore, Apple says iPhone 4S has “up to seven times faster graphics” versus the advertised “nine times faster graphics” on the iPad 2 – another proof that the two device’s graphics processing units are not clocked the same. Authors Anand Lal Shimpi and Brian Klug explain:


Chart courtesy of Anandtech

A lower clock not only means higher yields from the factory, but likely a lower operating voltage as well. Dropping a CPU’s core voltage, yields a greater-than-linear decrease in power consumption, making the marginal loss in clock speed a good choice. At a lower operating frequency than its Android competitors, Apple does have to exploit its strengths in software to avoid any tangible performance penalties. Apple has traditionally done this very well in the past, so I don’t expect the loss of frequency to be a huge deal to the few who do cross-shop iOS and Android.

GLBenchmark 2.1 (see results at the bottom of the article) paints the iPad 2 as having a 21 percent performance advantage over the iPhone 4S, stemming from different clock speeds. All said, both iPad 2 and iPhone 4S are well-equipped devices and are more than capable to run the latest games and graphics-intensive applications “at well north of 30 frames per second”. Summing up, game developers will likely optimize graphics in their titles for the iPhone 4S rather than for the iPad 2 in order to avoid the undesired performance penalties on the iPhone 4S.


Chart courtesy of Anandtech

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