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The search for the secret sauce in Apple’s A4 chip

by Scott Bicheno on 6 April 2010, 10:06

Tags: Apple (NASDAQ:AAPL)

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A mystery blend

Back when the iPad was first launched we thought the most remarkable thing about it was that is uses the first Apple-branded chip, called the A4.

It was always a fair assumption that the CPU core would be based around an ARM design, not only because the only real alternative would be for Apple to design its own chip microarchitecture from scratch - a la Qualcomm or Marvell - but because iPhone apps will work on the iPad, implying the A4 is pretty similar to the chip in the iPhone.

The latter is manufactured by Samsung, but designed by Apple and is generally accepted to pair the ARM Cortex A8 CPU design with Imagination Technology's POWER VR SGX  530 graphics core - in that respect pretty similar to the Texas Instruments OMAP 3430, which runs phones such as the Nokia N900.

Incidentally, Apple owns 9.5 percent of the shares in Imagination (Intel owns 16 percent) and now is rumoured to have bought Intrinsity, a fabless semiconductor company that specialises in optimising ARM designs and recently collaborated with Samsung on its Hummingbird SoC.

Electronic DIY site ifixit.com has partnered with reverse engineering company Chipworks to take the iPad to pieces and try to work out what the A4 chip is made of. While they still couldn't definitively conclude which microprocessor designs Apple had used, they found it has a single core, and so the assumption is that it's a Cortex A8, rather than the multi-core A9. They had to look at comparative benchmarks to deduce the GPU and came to the conclusion it uses the SGX 535. In other words: nothing very new.

Talking about benchmarks, tech site AnandTech had an initial go at testing the speed of the iPad by looking at how quickly it loads websites. It also compared it to the iPhone 3GS and the Nexus One, which runs on the Qualcomm Snapdragon SoC. While there are various other factors that could affect this speed, such as the modem, the OS and the browser, the iPad was found to be quicker than both.

But, crucially, the most critical benchmark of all has been completed and the iPad passed with flying colours. Those nutters over at Blendtec have wasted no time in asking of the iPad: will it blend? The clip below gives you the answer.


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