In-depth look at the A4 chip powering the Apple iPad

Tue, Feb 2, 2010


MacLife takes an in-depth look at the A4 chip powering the Apple iPad:

The fruits of Apple’s 2008 acquisition of P.A. Semiconductor finally saw the light of day when Steve Jobs unveiled Apple’s iPad. Underlying the sleek user interface and minimalist hardware is the Apple A4. The A4 is a system-on-a-chip (SoC) running at 1GHz. No mere CPU, the A4 includes integrated 3D graphics, audio, power management, storage and I/O interfaces.

The A4 is actually built around a CPU core based on the common ARM Cortex A9 CPU, a 32-bit core that comes in several different flavors, with different numbers of cores.

Reports have indicated that when Apple purchased PA Semi back in 2008, the team was subsequently split up into parts, with one focusing on developing ARM-based processors for iPhones and iPods and the other tasked with developing a processor for what would eventually become the iPad.

Before being acquired by Apple, PA Semi was renownked for churning out extremely efficient processors that used up relatively little power. It was this expertise that presumably led to the iPad’s impressive 10-hour battery life, which is quite astounding considering its large display.

Getting 10 hours of continuous battery life out of a 1GHz CPU using a 25Watt-hour battery requires aggressive power management. Indeed, the entry level MacBook is rated at only 7 hours with a 60Watt-hour battery.

Of all the hands-on reviews of the iPad thus far, the common thread running throughout is that the speed is just blazing – so much so that it makes the speedy iPhone 3GS look slow in comparison. If the next iteration of the iPhone, which Steve Jobs has already labeled an “A+ upgrade” comes with a new in-house processor from Apple, the next-gen iPhone may very well blow the competition out of the water.

MacLife concludes:

The graphics and audio components are likely licensed from PowerVR, including the PowerVR SGX GPU and PowerVR VXD for audio and video. These are all integrated into a single chip, although flash memory, networking and other components are on separate chips.  The A4 is actually built by Samsung, most likely using a 45nm manufacturing process.

The PowerVR SGX is a capable GPU, offering pretty decent 3D graphics. However, the iPad’s relatively low resolution (1024×768) is probably tied to a combination of limited video memory, and the fact that the chip’s raw pixel-pushing performance just isn’t up to pushing pixels at acceptable frame rates above that 1024×768 resolution. That said, at this resolution the SGX is a solid performer, and the iPad is likely to offer substantially better gaming performance, and a more robust gaming experience, than an iPhone. It’s quite possible that gaming will be the iPad’s killer app.

While much of the reaction to the iPad has bordered on the negative, a good number of developers are enthusiastically looking forward to the iPad and believe that its 9.7-inch multitouch screen will open an entirely new world of possibilities for apps.


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