Tuesday, February 2, 2010

Apple's New Chip on the 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. In typical cases, companies like Apple actually license the CPU design -- rather than paying $278 million to acquire the whole company! -- then are free to modify and integrate it as they see fit. It’s much different than the model for Mac desktop or laptop computers, in which the CPUs are wholly Intel products.

One of P.A. Semiconductor’s key principles was to design high levels of power efficiency into all their CPUs, which is probably one of the key reasons for Apple’s interest in the company. 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.

Apple hasn’t disclosed many specifics about the A4, so it’s unclear as to how many CPU cores it actually has. The A4. 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 (1024x768) 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 1024x768 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.

The ability to integrate custom features and functionality onto a single chip is what allows the iPad to be as compact as it is. While pundits have quipped that the iPad is just a big iPhone (or iPod Touch, depending on model), that’s not far from the truth. The internals of the iPad have more in common with a smart phone than a Mac.

The iPad, which essentially replaces much of the function of a low-end PC, needs other chips as well, of course. There’s storage -- in the form of flash memory -- plus Wi-Fi networking, GPS and 3G wireless cellular network capability.

So What Does This All Mean?

Using the A4 gives Apple -- legendary for wanting to tightly control its hardware and software destiny -- even more control over its hardware. Future iPads will almost certainly use descendants of the A4.

The use of the A4 inside the iPad also strongly suggests that the next iPhone will use a derivative of this chip. Designing a custom SoC isn’t cheap, so it makes sense for Apple to take further advantage of its $278 million investment. We’ll likely see higher resolution displays and higher clock speeds in even thinner and lighter form factors over time. However, some of these advancements will also be dependent on the evolution of other technologies -- like better displays.

It’s also likely that the A4, or some derivative, will be used in the next generation iPhone. Over time, this would allow Apple and its developers to develop to a single code base, rather than having to manage multiple different versions for different CPUs.

So that’s the story on what could happen. But what’s not likely to happen? First, the A4 won’t show up in future MacBooks or iMacs. MacBooks and iMacs will still use Intel-compatible CPUs, not some version of the A4. While Apple does like to control its destiny, modern Mac applications require very high-performance CPUs and higher-end graphics than is likely capable with a system-on-chip.

Also unlikely: you won’t see an Intel Atom in an Apple system of any kind.

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