mldebo

ARS speculates
Quote

Why has Apple been so secretive about the A4? Why hasn't the company presented a paper on the device at ISSCC, or published a whitepaper?

I don't know the answer to these questions, but given what I do know about the A4, I suspect that the reason is twofold. First—and this is purely my supposition—Steve Jobs just loves secrets. The A4 no doubt gives him that special, "I have my very own custom SoC that you don't know anything about" feeling, and if we're honest with ourselves, wouldn't we all love to know what it's like to have that feeling? I know I would.
原帖地�: TechSpott - Computer and technology forums http://www.techspott.com//showthread.php?p=552

The second, and perhaps most likely reason behind Apple's silence, is that the A4 just isn't anything to write home about—and on this second point, I actually know a thing or two. If Apple were to tell you what's in the A4, most of the focus would be on what the chip is not, rather than on what the iPad is.

As I watched the videos and read the reports of the iPad in action at the launch event, I was thoroughly convinced that the device was built on the out-of-order Cortex A9, possibly even a dual-core version. But it turns out that the the A4 is a 1GHz custom SoC with a single Cortex A8 core and a PowerVR SGX GPU. The fact that A4 uses a single A8 core hasn't been made public, but I've heard from multiple sources who are certain for different reasons that this is indeed the case. (I wish I could be more specific, but I can't.)

In all, the A4 is quite comparable to the other Cortex A8-based SoCs that are coming onto the market, except that the A4 has even less hardware. The iPad doesn't have much in the way of I/O, so the A4 itself can do away with the I/O that it doesn't need. In contrast, the typical Cortex A8-based SoC has more I/O hardware than a mobile phone can use, because you never know what customers will need which interface types.