The iPad CPU: Details on the Apple A4 | Hacker News Reader

The iPad CPU: Details on the Apple A4

maclife.com

39 pointsprofquail26 comments

This is less 'details' and more 'guesses'. There have also been (equally unconfirmed) reports that it uses a different GPU (an ARM Mali).

I stopped reading after I noticed the word "likely" is used 7 times in the single page article...

Pure speculation on my part, but I wonder if Apple can and/or has baked trusted computing into the A4 silicon.

By controlling this much of the hardware, Apple can make it next to impossible to jailbreak their devices.

Wouldn't be surprising at all. http://www.arm.com/products/security/trustzone/index.html

There was nothing stopping them before: both generations of iPhone / iPod touch chips were bespoke SoC hardware too, just via Samsung.

The core of the piece:

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!

If Arm Holdings could be acquired for $278m, I'm sure Apple would have done it by now. Unfortunately for Apple, though, its market cap is actually in the $2-$2.5bn range.

Granted, they do have $30bn+ in cash lying around...

It's more likely Steve had $278M in his expense account.

At one time Apple used to own 40%+ of ARM (for the Newton) and what we know of as ARM holdings was basically a joint venture between Acorn, Apple, and VLSI. Back when they really needed cash Apple was probably pretty glad they had such a large chunk of a company whose value at the time was appreciating faster than Apple's...

The point is that Apple bought PA Semi for $278M. It would be unusual to spend so much money for a processor company and then turn around and use off-the-shelf ARM processors.

A PA VP told me Steve Jobs asked them to drop their nearly-finished Power design immediately to build AAPL a custom ARM SoC; they said no, so he bought them, to help them say yes. He probably could have poached their stars for a lot less than $278M, but I guess he was in a serious hurry, or just viewed $278M as not worth the hassle.

If he'd tried the "poach" approach, he'd probably not have gotten intact teams and there would have been a lot of unhappy people.

Buying the entire company almost certainly worked better, another sign that Jobs "gets it" even without being a hardcore techie. A one of a kind, I think.

Perhaps. But if you look at the comps, PA investors got a sweet deal.

I remember when Apple brought out the Macbook Air - and it sounded like a huge partnership between Apple and Intel. What is the relationship going forward?

I don't have any inside scoop here, but a huge partnership between Apple and Intel and an ARM-based iPad are not mutually exclusive. Most people acknowledge that, to get the kind of energy efficiency and battery life that people are starting to expect in mobile devices, current x86 parts are not a good solution. Nonetheless, we are stuck with x86 for anything that wants to run most existing desktop/laptop software until we come up with a virtualization, cross-compilation, or binary translation scheme that is efficient enough.

If Apple wants to continue selling Mac Pros and Macbooks, they will probably stay Intel for some time. Until Intel comes out with a part that can get Apple anywhere close to the many hours or even days they require for their mobile devices, Apple has no choice but to look elsewhere, and I can't see that as a reason to end a partnership on desktop/laptop processors.

Do you remember when some Intel Execs trashed the ARM chips, as used in iPhone and iPads, as not being able to handle "the real internet" (Intel code for Flash support).

Apple got a public apology acknowledging that Intels chips couldn't hold a candle to ARMs in this area:

http://news.cnet.com/8301-13579_3-10074228-37.html

So it seems like they're happy to keep Apple sweet as long as they use the Intel chips in the appropriate devices.

The "system on a chip" Atom CPU is still under development and needs a lot of work (ie. time), whereas ARM is here today.

A 1.6GHz Intel Atom spanks an entire week of lunch money out of a 1 GHz ARM, in terms of CPU performance. No doubt AAPL can mostly hide that with faster SW, relative to Windows Vista/7. But I would hate to compile anything on A4, whereas, a $200 Linux netbook is fine for most development.

IMO it's sad for something iPad's size to not have a reasonable native development environment.

A 1.6GHz Intel Atom spanks a 1 GHz ARM

Not necessarily; ARM claims that the Cortex A9 is the one doing the superscalar out-of-order spanking and I'm inclined to give them the benefit of the doubt.

I'd love to see citations on both rphlx's and wmf's claims. Not trying to sound mean - I'm honestly interested in the future of low-power computing and I kind of hope ARM wins.

Here is one link: http://perspectives.mvdirona.com/2009/09/16/ARMCortexA9SMPDe...

Also Anandtech on the Cortex A9: http://www.anandtech.com/gadgets/showdoc.aspx?i=3714&p=3

and the pages around that.

Here is my reasoning --

An Atom Z530 1.6GHz core has almost exactly 2X the Dhrystone MIPS of a 1.0GHz ARMv5TE-based network SoC (I actually ran it; those are not bogus vendor marketing #s).

A9 probably has much higher IPC than ARMv5 -- but I doubt it's high enough to beat an Atom running at 60% higher frequency; that is a hell of a gap to close architecturally. I also suspect Atom has higher DRAM bandwidth; the A4 pkg looks a bit small for x64 DRAM. Finally, A4 may or may not have more than 1 core; Atom definitely has 2.

I am talking pure performance, not performance per watt, which is not interesting to me in this situation. I can almost always find AC if I'm using something iPad-sized.

That's the whole point here- by preventing multitasking it's possible to give every single app massive resources, relative to an Atom chip. No YouTube videos buffering with Skype running in the background and three Word docs fired up.

The perceived performance is phenomenal, and that's the whole point. As for native development environments, no one gives a shit outside of HN- that's what Macs are for. Pony up the extra $700 and you're good to go with a MBP.

Unfortunately, Atom uses two weeks worth of spanking energy to get that week out of ARM.

I read somewhere that the A4 has an ARM MALI graphics processor, not an SGX.

That guy also has no idea what he's talking about.

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