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Apple's A4 Processor is Based on Cortex A8, Not A9?

t0mat0

t0mat0

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Aug 29, 2006
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We await confirmation of this, but some in the tech world seem to be adamant that Apple's going to use a stripped down single core A8 chip within its A4 chip (helping with speed).

http://arstechnica.com/apple/2010/02/meet-the-a4-the-ipads-brain-not-quite-ready.ars


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.
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Article Link
https://www.macrumors.com/2010/03/01/apples-a4-processor-is-based-on-cortex-a8-not-a9/
Apple's A4 Processor is Based on Cortex A8, Not A9?




120133-apple_a4_chip_500.jpg


Ars Technica reports on Apple's new A4 chip which was introduced alongside the iPad in January. Apple has released few details about their custom chip design, though many expected it to have adopted the latest Cortex A9 multi-core design.

Ars Technica's Jon Stokes counters this belief with multiple sources who indicate the new processor is actually based on the Cortex A8 -- the same design as the current iPhone and iPod Touch.
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.)
Click to expand...
We've heard similar whispers which make use believe this report is true. The iPad A4, of course, runs at a higher clock speed (1GHz) than the processors found in the iPhone (600Mhz) and iPod Touch. Stokes goes on to speculate that the PA Semi team could have added their expertise in lower power consumption, and the A4 could find its way in a future iPhone release.


Article Link: Apple's A4 Processor is Based on Cortex A8, Not A9?
 
Eso said:
It's an A9 chip, reported weeks ago.
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Yes, and? This is a new report, saying that it is an A8, from a blogger who is highly respected as a chip expert who typically has insider knowledge. Apple never announced what it actually has. Further, it won't be possible, I don't believe, to confirm by simply taking the thing apart. There will be a little square of silicon that says Apple A4 on it. Developers may, however, be able to probe it with test code to see what it can do, like for instance, if it is dual-core.

I'm skeptical of the article here:

Apple's 30-pin connector supports TV-out, [redacted start] but no external display attachment has been announced for the device, so it's possible that the SoC forgoes the common TV-out I/O block and related support for a secondary display [redacted end]. (Apparently the latest rumors from the SDK indicate that there is external display support, and at least one company has announced an adaptor.)
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Even though he corrected the part at the end, it's a big oversight. It's not just rumors though! His "corrected" version is bunk. APPLE has component and VGA adapters for the darn thing! Not rumors, but on their website. Geeze.

However, if this article turns out to be true, I'll be fairly disappointed. I'm worried about future proofing as the first gen iPhone can get pretty laggy on 3.0. My wife uses my old one and it can be a pain to type on and play certain games. I just can't see Apple using such an old processor design! Most smartphones this year will use A9 variants, and will therefore be faster than an iPad, which would be sad. I don't want games lagging on my 1024x768 screen, which is somewhere around 5 times more pixels than an iPhone on a processor that is 67% faster based on mhz alone. Sure "A4" enhancements might help, but not as much as an A9 with dual-cores and new architecture.

In addition, weren't the power saving features supposed to be primarily due to an A9 based Apple A4?

This pushes me from "getting an iPad" to "thinking about maybe not getting an iPad". I don't know. V2 is starting to sound better every day. Crap, I'll probably buy them both anyway and give my wife the 1st gen. Who am I kidding?
 
This sounds about right as Apple is slow to adopt new processor technology typically.
 
This is very interesting... I guess it to be a power consumption thing. The fact that they made it themselves with the software makes it seem as snappy as it is. (But would the A9 make Safari snappier?)
 
Looked plenty fast enough in the videos, not like I'm doing Handbrake rips on it.

Interesting tid bit but is the processor really important in a product like this?
 
At the end of the day this is largely irrelevant as these new devices and their app stores mean that you buy software that just works on the device as supplied. As long as the processor is up to the job then who cares what it is anymore.
 
Existing thread: https://forums.macrumors.com/threads/871736/

Guess I'll repost my thoughts...

I'm skeptical of the article here:

Apple's 30-pin connector supports TV-out, [redacted start] but no external display attachment has been announced for the device, so it's possible that the SoC forgoes the common TV-out I/O block and related support for a secondary display [redacted end]. (Apparently the latest rumors from the SDK indicate that there is external display support, and at least one company has announced an adaptor.)
Click to expand...

Even though he corrected the part at the end, it's a big oversight. It's not just rumors though! His "corrected" version is bunk. APPLE has component and VGA adapters for the darn thing! Not rumors, but on their website. Wow.

However, if this article turns out to be true, I'll be fairly disappointed. I'm worried about future proofing as the first gen iPhone can get pretty laggy on 3.0. My wife uses my old one and it can be a pain to type on and play certain games. I just can't see Apple using such an old processor design! Most smartphones this year will use A9 variants, and will therefore be faster than an iPad, which would be sad. I don't want games lagging on my 1024x768 screen, which is somewhere around 5 times more pixels than an iPhone on a processor that is 67% faster based on mhz alone. Sure "A4" enhancements might help, but not as much as an A9 with dual-cores and new architecture.

In addition, weren't the power saving features supposed to be primarily due to an A9 based Apple A4?

This pushes me from "getting an iPad" to "thinking about maybe not getting an iPad". I don't know. V2 is starting to sound better every day. Crap, I'll probably buy them both anyway and give my wife the 1st gen. Who am I kidding?
 
All I can say is that I really don't understand processors, how they work, and what all this means :)
 
Smart. It has an Apple logo, so a lot of Apple users are going to buy it anyway, so need to spend more money on a more powerful chip.

Wasn't it reported that they spent 1 billion dollars developing this?
 
It makes a lot of sense since Apple probably have had this device under development since before A9 was released. I think it's great that A4 seems to be pretty capable as it is so a multicore A9 version will be plenty powerful in the future.
 
talkingfuture said:
At the end of the day this is largely irrelevant as these new devices and their app stores mean that you buy software that just works on the device as supplied. As long as the processor is up to the job then who cares what it is anymore.
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Actually, at the end of the day it means that developers won't be making any apps that would use the extra power.
 
Chundles said:
Looked plenty fast enough in the videos, not like I'm doing Handbrake rips on it.

Interesting tid bit but is the processor really important in a product like this?
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Plenty fast with what? Apple-made apps? iPhone apps?

I'd like to see a comparison of an A8 vs A9 for video games and photo editing. Yeah, this thing is made for photo editing. It's got camera adapters and an IPS display which is probably better than most people's own monitors which are likely to be TN or MVA based. As for iPad specific games, pushing 5x the pixels at 1024x768, it seems like it could really benefit from a faster chip. Is the PowerVR chip in this thing magical enough to compensate? The iPhone 3GS, I believe, has a down-clocked 800mhz processor @ 600mhz. So this thing is at least what, 67% faster + Apple optimizations? Doesn't seem like enough of an advantage over an iPhone, with a much higher res display. Hmmm.
 
A conservative approach will let developers focus on supersizing not compatibility. Apple TV also in the 1 Ghz club but with good OLD Intel.
 
macduke said:
Plenty fast with what? Apple-made apps? iPhone apps?

I'd like to see a comparison of an A8 vs A9 for video games and photo editing. Yeah, this thing is made for photo editing. It's got camera adapters and an IPS display which is probably better than most people's own monitors which are likely to be TN or MVA based. As for iPad specific games, pushing 5x the pixels at 1024x768, it seems like it could really benefit from a faster chip. Is the PowerVR chip in this thing magical enough to compensate? The iPhone 3GS, I believe, has a down-clocked 800mhz processor @ 600mhz. So this thing is at least what, 67% faster + Apple optimizations? Doesn't seem like enough of an advantage over an iPhone, with a much higher res display. Hmmm.
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The apps demonstrated during the keynote, specifically Need For Speed which looked really nice.
 
macduke said:
I don't want games lagging on my 1024x768 screen, which is somewhere around 5 times more pixels than an iPhone on a processor that is 67% faster based on mhz alone. Sure "A4" enhancements might help, but not as much as an A9 with dual-cores and new architecture.
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Primarily you need more fillrate for a larger screen

-> higher frequenzy and more bandwidth

PowerVR
SGX 535 = 2 ALUs (USSE1), 2 TMUs
SGX 540/545 = 4 ALUs (USSE1), 2 TMUs
SGX 543 = 4 ALUs (USSE2), 2 TMUs

If fillrate is the primary target, the SGX 535 has the best chances to be in the A4, because it has a smaller DIE and so it can reach higher frequenzy.
 
baryon said:
All I can say is that I really don't understand processors, how they work, and what all this means :)
Click to expand...

My understanding: People thought the iPad would have an ARM Cortex A9 processor, but it uses the older ARM Cortex A8 design.

From what I've read (not much) the Cortex A9 has out of order execution and speculative issue. Out of order execution allows the CPU to reorder instructions to avoid stalling for various reasons (cache misses and data dependencies for example). Speculative issue allows a reduction in stalling on branch instructions because instructions may be sent to functional units based on a prediction of the direction of the branch. Without speculative issue, instructions must wait for the branch prediction to be confirmed accurate.

Understandably people are disappointed that the chip isn't the newer version that has these features.
 
Would it really need to be dual-core? In every single video of the iPad I see absolutely no lag. Dual-core would just consume more battery (yes, if it was dual-core it'd pretty much be no question as to whether multi-tasking is included, but still).
 
macduke said:
This pushes me from "getting an iPad" to "thinking about maybe not getting an iPad". I don't know. V2 is starting to sound better every day. Crap, I'll probably buy them both anyway and give my wife the 1st gen. Who am I kidding?
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Why would it?

It sounds like Apple took an off the shelf SoS and supercharged it. Why deal with the inefficiencies of an early design of the A9, and instead supercharge more proven technology.

All the people who have had hands on with the iPad say it is very fast, who cares what is under the hood if it does its job properly.

Plus, instead of thinking about "future proofing", think craigslist. I routinely sell old Apple gear for very high return. In some cases it is possible to "rent" apple gear for about 10% per year you keep it and I suspect the iPad will be the same.

Right now I am buying a new 17" MBP every time they announce a new one. I typically buy a new one for about $3200 and sell the old for ~$2900 (usually with minor upgrades). After the first year of pain buying the unit, I now pay only $300 per year for a bleeding edge top of the line laptop. This next upgrade will be the harshest since I skipped the uMBP, but still should be able to sell my current unit for $2500 or so when the new processors come out (hopefully) soon. This is cheaper than buying a new netbook every year for a MUCH better machine (and how many netbooks can take the abuse of a hard year of use?).

When the next generation comes out, sell the old and buy the new, future proofing hardware is what we did in the 90's.
 
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