In another one of my follow up posts to the iPad, I want to talk a little bit more about the hardware in the device. As some may remember, Jobs made a point of explaining that the iPad doesn’t just use off-the-shelf ARM hardware like many other platforms, but runs their “custom silicon” developed in house. Now, from the get go, most figured this was going to be hyperbole. “Custom silicon” probably just meant they selected all the controllers, processing, audio, and graphics cores themselves and then sent the parts to Samsung for fabrication (Samsung has made most of Apple’s mobile chips in the iPod and iPhone). But ever since Apple acquired P.A. Semi, a custom chip designer, there was the possibility they had done some significant power optimizations or what have you, it was unknown because Apple hadn’t released any white paper on the chip. What was known was that it was definitely an ARM derivative running at 1Ghz. It seemed probable that it was the ARM Cortex-A9, the latest from the company, possibly even a dual core solution. Initially it was rumored that the GPU was another ARM solution: their Mali graphics core. However, recent information has proven that it uses a far more powerful PowerVR SGX GPU like in the iPhone. RAM was unknown but I’d figure around 512MB if the iPhone has 256MB.
However, if we are to believe this article from Ars Technica, these estimations are off. Pathetically so. A4 isn’t that special, A4 is actually quite mundane. Any special design is in what it doesn’t have, not what it does. According to the article which I am inclined to believe due to the professional reputation of Ars Technica, A4 is comprised of a single core Cortex-A8 (A8 lacks out-of-order, a crucial performance feature) at 1Ghz. This is the same core in the iPhone, just 400Mhz faster. The graphics core is indeed still a PowerVR SGX, though I’m willing to bet it is no better than what is in the iPhone. Any optimizations in the chip is really in what it lacks. Apple’s team has taken out large amounts of I/O processing since the iPad has very few inputs or outputs. It lacks logic for a camera, more than one USB port, and other bits not needed. So yes, the chip is probably more power efficient than other A8-based SoCs on the market, but with the power demands of the iPad’s screen, it probably doesn’t help much. Such tight optimization really shows benefits in the phone sector.
So, what does this really all mean? In general, it just makes the iPad look far less impressive than it did (I know, seems hard to imagine). But you’ll recall my initial post on the iPad where I was very excited by the prospects of the A4 chip. Now, it just seems like another knock against the device. The fact that this chip seems so rudimentary brings to question how on earth Apple could have spent a reported $1 Billion on its development. Placing things in perspective, Apple choosing an A8 over an A9 makes it lose serious points against competitors. A8, in terms of performance, can be about equal with Atom clock-for-clock. But Atom has a higher clockspeed on many models, though at the expense of battery life. Other devices are planning to use Nvidia’s Tegra 2 which comes with a dual-core Cortex-A9 solution. The picture being painted here is that after the woes over Apple’s software choices, now we have trepidation over its hardware capabilities. That said, the weaker hardware could more appropriately explain Apple’s choice for not including multitasking in the iPad’s OS. But that is just another example of Apple’s tremendous oversight on their design.
So the question remains, what is PA Semi being used for? Well, probably just this: making custom tailored SoCs for Apple instead of having to look through other vendors for their needs. A4’s lack of hardware is not any knock against the Apple Chip Design team explicitly, but rather showing how much optimization has been made. The fact that A4 is weaker than once thought shows Apple did not have enough foresight when developing the chip (it was apparently manufactured back in September of last year). But for the future, if and when Apple gets wise and pairs their SoCs to more powerful hardware, we can expect for the same level of power optimization and hardware tailoring to be done. As well, since A4 really is entirely like the iPhone’s chip, a future with the iPhone using the A4 seems far more likely. And that, at least, is something to be interested in.
Now, in the end it’s really all about the software right? That’s the point of these devices, that hardware alone doesn’t have to mandate who wins. But given the fact that the iPad is more and more looking like absolutely nothing more than a giant iPhone in now every single respect, there’s so little to be excited about. Again, here’s hoping for a major rethinking under the iPad v2. And maybe for an end to these articles too?