The big mystery behind the recent Apple iPad announcement is the A4 processor that powers this touchscreen, “tablet” PC. What’s in it, and why did Apple design its own system-on-chip (SoC) as opposed to using off-the-shelf hardware? First, I offer some tidbits of information and speculation gleaned from various on-line articles, and secondly, I have a few thoughts about what the A4 tells us about the future of chip design and EDA.
As noted in a Cadence Community blog by Jack Erickson, a tablet PC has some special requirements. It has to be more graphics-intensive than a traditional PC, requiring more CPU horsepower. It also needs longer battery life than a PC, with a smaller and lighter battery. This is hard to do with off-the-shelf hardware.
About all the Apple has publicly said is that the A4 is the “most advanced chip” the company has ever used, and its power efficiency gives the iPad up to 10 hours of battery life. The Apple iPad spec sheet calls it a 1 GHz “custom designed, high-performance, low-power system-on-a-chip.” Apple has IC design expertise from its April 2008 purchase of low-power processor developer PA Semi.
Here’s what a few on-line articles have said:
New York Times
This article notes that Apple has taken a bold step by designing its own processor, but has also taken on extra engineering costs. It notes that several key PA Semi chip engineers have already left Apple. The article also says that some analysts believe Samsung is manufacturing the A4.
Suzanne Deffree’s blog states it is “assumed” that the A4 came out of the acquisition of PA Semi. But a blog comment notes that it takes at least 12-18 months to design, debug and manufacture an SoC like the A4, and that the design was likely underway before the PA Semi people came on board at Apple.
A CNET reporter describes the A4 as an SoC integrating a main processor, a graphics processor, a memory controller, and other functions. The article says the core processor is from ARM, maintaining compatibility with the iPhone.
There’s some interesting history here. The article notes that PA Semi outlined a vision for an SoC PowerPC architecture, called PWRficient, in 2005. The sole member of the family was released in 2007; it ran at 2 GHz with an average 13 watts power consumption. Meanwhile, Apple was struggling to put a G5 processor into a PowerBook in 2005 and was running into thermal challenges. “It was in these dire circumstances that Apple took notice of PA Semi,” the article states.
Bright Side of News
This article claims that the A4 uses an ARM Cortex-A9 processor (like the Nvidia Tegra and Qualcomm Snapdragon) and an ARM Mali GPU. It describes the A4 as “mostly” ARM IP.
As time goes on, I’m sure there will be “teardowns” that will tell us a lot more about what’s inside the iPad and what’s been integrated onto the A4. Meanwhile, here are three thoughts about what the A4 might tell us about the future of chip design in the mobile consumer industry:
First of all, that custom chip design has a future. Despite all we’ve heard about embedded software becoming the main differentiator for electronic products, you still need to design custom hardware when you have a high performance demand, an extreme low power requirement, and/or a very small or unusual form factor.
- Even for very demanding applications, custom hardware development is as much about integrating existing IP as it is about creating new IP from scratch. The focus of chip design is shifting to IP integration, and the EDA industry needs to provide tools and methodologies specifically aimed at that task.
- Power trumps everything in an application like the iPad. About the only thing Apple has revealed about the A4 is the long battery life it allows. PA Semi’s claim to fame was low-power processor design. Put it all together and power was likely the primary driver behind Apple’s custom SoC development effort.
The EDA industry can be reassured that there will always be custom hardware design. But the growing demand for IP integration and power management will place heavy demands on next-generation EDA software.