“Last week, I had all but conceded that the A4 was Cortex-A8 based, but developments this week demonstrate that whatever the A4 is, it is not merely a re-hash of the Samsung iPhone processor, as so many have concluded,” Mark W. Hibben blogs for Technomicon.
“A more consistent theory is the one I have offered in the past: the A4 is derived from the PA Semi PA6T, which is a dual core Power Architecture processor,” Hibben writes. “The reason why the performance is only so-so is that the A4 is still functioning as an ARM processor emulator. A future update to iPhone OS will undoubtedly take care of this problem.”
“Aside from Apple’s natural secretiveness, probably the main motivation was to avoid scaring off the developer community. Developers have been understandably leery of major platform changes in the past. When Apple switched to PowerPC from Motorola 68K, many developers simply dropped out rather than upgrade their development tools. With Apple providing the development tools, this really isn’t a problem any more, but I still hear developers grumble at the mere mention of a processor architecture change. They shouldn’t worry,” Hibben writes. “The change in instruction set should be fairly transparent to the developer in Xcode. Most of the work to adapt to iPad that developers have to do involves the larger screen size, an adaptation they would have to make in any case.”
Hibben writes, “The perception that the A4 was Cortex-A8 based had me very worried about the future of the iPad and Apple in general. It appeared that iPad was about to be waylaid in the market place from two sides. On the one side will be Cortex-A9 based tablets and smart phones running Google OS and Flash 10.1 for Mobile. On the other side will be Windows Netbooks running Windows 7 and the new 32 nm process Intel Atom processors that are right around the corner. This would have been very stiff competition for the humble ARM Cortex-A8. Fortunately, Apple does not appear to have burdened itself with such a mill stone.”
Full article, the 11th week in a series of A4 posts, here.
[Thanks to MacDailyNews Reader “KenC for the heads up.]
At least the writer has the decency to admit being wrong before…
Respect
“the A4 is still functioning as an ARM processor emulator”
Wow, virtual processor platform… hmmm, that would be cool.
Mark W. Hibben. You should know what you’re writing about before writing.
This actually fairly typical of the entire design approach for Apple…maintain a measure of backward compatibility but build devices that the rest of the world will catch up to. This not only makes these systems more future proof, they actually IMPROVE over time (to a point) not fall into obsolescence in a year.
First post where he posits the A4 might be a PA Semi in week 2, after
Steve’s keynote:
http://www.technomicon.com/iPad_Saga_-_Week_2.html
Explaining in week 3 the choices Apple management faced in choosing a SOC
for the iPad, and how the timeline forced them to an ARM8 or PA Semi:
http://www.technomicon.com/iPad_Saga_-_Week_3.html
In week 6 he explains how Apple could use the PA Semi A4 SOC-family in the
iPhone and Macbooks:
http://www.technomicon.com/iPad_Saga_-_Week_6.html
In week 10, he points out the memory controller on ARM8s are 32-bits wide, while the A4 is 64-bits wide.
http://www.technomicon.com/iPad_Saga_-_Week_10.html
Here is the post, Week 11, where he states the A4 is not an ARM as the process width and die size don’t match up with an ARM8:
http://www.technomicon.com/iPad_Saga_-_Week_11.html
I don’t know if anyone recalls, the story from last week, when the new Macbook Pros came out that someone wondered if Apple could use an A4 in a Macbook, well, in Week 6 above, the writer shows that it might be possible with a 4-core A4 at 1.5Mhz, or something like that.
@bart
Wow, virtual processor platform… hmmm, that would be — SLOW
There is no why that they are going to be able to emulate the ARM processor with reasonable speed on another mobile processor. I doubt, you could get reasonable speed on a desktop processor.
It would be “so so” performance in comparison to the iPhone. It would be dog slow.
Emulation is extremely inefficient. The fastest parts of a processor, such as setting registers become a huge bottleneck in emulated environments.
Wasn’t there a story just a week or two ago that all the big names from PA Semi had moved on to other opportunities, and that the acquisition was a flop?
He’s also wrong about “It appeared that iPad was about to be waylaid in the market place from two sides.”
@edster,
Not necessarily. It depends on where the emulation is taking place. If it is at the user-code level (similar to what happened during the switch from MC680x0 to PowerPC), then you are correct, it would fairly inefficient. But it could be done (all or partially) in the A4 firmware. Just like with nearly every major processor since the 1990’s, the ISA is virtual, with the actual hardware running the firmware to give the appearance of the ISA. This is really not new, either. When IBM came out with the 360 series in the 60’s & 70’s, they had a range of actual hardware (with appropriate throughput and price), but they all “looked the same” as far as programming them due to the firmware. I’ve heard of a case where the IBM360 firmware was re-written to emulate an IBM 7040.
In any case, the end result is that a firmware upgrade in the future could result in a more streamlined throughput for anticipated changes.
@ John–
No. The acquisition of P.A. Semi was for their technology.
Several of their engineers went on to start a new company, which has also since been acquired by another company, which people have speculated could be Apple.
Nowhere in that scenario is the word “flop.”
It seems clearer every day why Steve doesn’t want to stack a lot of runtimes on top of his OS.
I always thought that PA Semi doing an ARM design didn’t sound quite right. It’s in their DNA to do whatever they do with a Power chip. That’s what they’ve always done.
@TheConfuzed1: ComputerWorld speculates otherwise
This just doesn’t seem consistent with the objective of maximizing battery life. Smells wrong to me.
“…performance is only so-so…” ??? In all reviews it has been said that iPad is blazing fast.
@Pete: as a happy owner of an iPad, I can state that it feels blazing fast, but that I don’t think it really is all that fast.
Apple has done a great job of optimizing the user experience when navigating the home screens, and the responsiveness of the keyboard is usually solid, but loading heavier applications is still time-consuming.
Responsive, overall? Absolutely. Still a mobile device with a mobile-caliber processor? Yup.
If the iPad has a stealth PPC in it, that would be a hell of a trick. I’d love to see Apple finally ship a G5-class processor in a MacBook pro.
-jcr
Didn’t it strike anyone else as odd on why the iPhone OS 4 would not be available for the iPad until Fall if the A4 Chip was just an ARM processor? It did me, but, I never assumed it was an Arm Chip. The A4 was too fast, too math friendly to an ARM chip. My Assumption was that the A4 was either a new CPU Core design or a PA Semi Power CPU design. The delay in iPad update to iPhone OS 4 to just confirmed that. Apple is very good at parallel CPU development they did it (and are doing it with Mac OS X on Intel and Power) with the iPhone I’m sure that we’ll learn that it too as been developed in parallel for ARM and PA Semi Power.
Keeping all the developer code developed in XCode mean that it’s all Coco native code and for the developer becomes a non-issue as to the CPU used to run the code because Apple’s OS will do the hard work. The Power to Intel switch was hard for developers because so much of their code was still written for the Old Mac OS 8 &9;and was not Pure native OS X code, for all that Applications that were fully Mac OS X Native the transition was simple, straight forward and very painless.
Support any type of emulation or Byte Code translation Layer in the iPhone OS means that someone is going to suffer down the road. Because Applications built outside of X-Code will likely need a lot of work and even more code re-factoring as Apple Moves in new CPU designed down the road.
And the legend of PowerPC lives on forever
Everybody who believes that the Apple A4 is based on a single Core Cortex A8 have no strategic and technical understanding, but everybody who believes this chip is a disguised PowerPC must completely be crazy.
The “Power Architecture” is a broader category that includes PowerPC. If this is true, how interesting…
As I mentioned previously, I’ll speculate that the “4” in “A4” means it’s quad-core (not a series number). When the new iPhone appears, it will have an dual core “A2.” It’s likely that this is wrong, but it would be really cool if correct.
I suppose it is possible, but why on earth would they bother? I think this theory is lunatic thinking
Pass the crack pipe Mark.
Honestly, A4 based off the Pwrficient PA6T? You’d have to be on crack to think that’s practical.
PASemi was formed by ex-DEC folks who produced the StrongARM which, when produced, was significantly faster than any chip ARM designed, a record it kept for about the next 5 years. They know ARM. They’re more than capable of taking a stock reference ARM Cortex A-8 design and tweaking it.
Having a PPC chip emulate an ARM chip would be daft. It’d eat power.
His arguments are contradictory. Anybody who uses the GNU compilers know they are extremely capable of cross compiling (developing on one platform to provide binaries for another platform). So as long as Apple provided a set of consistent libraries, the developers should not be affected by chip sets.
Right now the Xcode that ships with SL provides compiles for x86/ppc (32-bit) and x86_64 (64-bit) architectures. The developer can pick choose which binary to provide. I doubt anyone can tell the difference when using Cocoa and Foundation tools for App development.
just my $0.02
I wish people would stop attributing magical powers to Apple, especially when they don’t have evidence.
The ipad is Samsung’s Hummingbird processor – a specially hardened version of the Cortex-A8. Power PC is not present.