Enter the ARM Cortex A8

This past weekend Palm introduced its highly anticipated Pre. While I’m still working on my review of the Pre, I can say that it’s the closest thing to an iPhone since Apple first unveiled the product two summers ago. In many ways the Pre is lacking in areas that the iPhone has honestly perfected, but in others the Pre easily surpasses Apple’s best.

One such area is raw performance. While both the iPhone and iPhone 3G use the same old CPU/GPU, the Pre uses TI’s OMAP 3430 processor. The 3430, like the SoC Apple uses, has both a CPU and GPU on the same package. Instead of the ARM11 and the PowerVR MBX-Lite however, the OMAP 3430 uses an ARM Cortex A8 core and a PowerVR SGX GPU. Both are significant improvements over what was in the original iPhone.

Thankfully, Apple fans don’t have to be outclassed for long - the newly announced iPhone 3GS uses a comparable CPU/GPU pair.

Although unannounced, the iPhone 3GS uses (again) a Samsung SoC but this time instead of the ARM11 + MBX-Lite combo it’s got a Cortex A8 and PowerVR SGX; just like the Pre.


A derivative of this is what you'll find in the iPhone 3GS

If the ARM11 is like a modern day 486 with a very high clock speed, the Cortex A8 is like a modern day Pentium. The A8 lengthens the integer pipeline to 13 stages, enabling its 600MHz clock speed (what I’m hearing the 3GS runs at). The Cortex A8 also widens the processor; the chip is now a two-issue in-order core, capable of fetching, decoding and executing two RISC instructions in parallel.

The ARM11 processor in the iPhone/iPhone 3G has a basic vector floating point unit, but the A8 adds a much more advanced SIMD engine called NEON. The A8 also has twice as many double precision FP registers as the ARM11. The addition of NEON and the improved vector FPU in the A8 makes the processor much less like the original Pentium and much more like Intel’s Atom. Granted, Atom is significantly faster than the A8, but it also draws much more power.

Caches also get a significant improvement. I believe Apple will be using a derivative of Samsung’s S5PC100, which has a 32KB/32KB L1 cache (I/D, we may see a 16KB/16KB config instead) and a 256KB L2 cache. The L2 cache, as you’ll remember from the first section, is a new addition to the A8; the ARM11 core didn’t have an L2.

  iPhone 3G (ARM11) iPhone 3GS (ARM Cortex A8)
Manufacturing Process 90nm 65nm
Architecture In-Order In-Order
Issue Width 1-issue 2-issue
Pipeline Depth 8-stage 13-stage
Clock Speed 412MHz 600MHz
L1 Cache Size 16KB I-Cache + 16KB D-Cache 32KB I-Cache + 32KB D-Cache
L2 Cache Size N/A 256KB

 

The combination of higher clock speeds, more cache and a dual-issue front end results in a much faster processor. Apple claims the real world performance of the iPhone 3GS can be up to 2x faster than the iPhone 3G, and I believe that’s quite feasible.

The new SoC is built on a 65nm manufacturing process, down from 90nm in the original hardware. However, power consumption should still be higher for the new SoC compared to the old one. ARM’s own site lists ~0.25mW per MHz for the ARM11 core but < 0.59mW per MHz for the A8. That’s for a 650MHz low power A8 core and I’m expecting 600MHz for the 3GS, that’s at most 3x the power consumption of the CPU in the original iPhone. So how can Apple promise better battery life?

The thing about these comparisons is that they don’t show the full picture. With the same battery capacity, running at full speed, the new iPhone 3GS would run out of juice faster than the existing iPhone 3G. But that’s rarely how people use their phones. Chances are that you’ll perform a few tasks before putting the phone back to sleep, and what matters then is how quickly you can complete those tasks.

Just under nine years ago Intel talked about a technology called Quick Start. Let me quote from our IDF 2000 Day 2 coverage (wow, that was a while ago):

“"Intel has figured out that it is best to use full CPU power for a split second to finish a task and then put the CPU to idle as this conserves battery life the best. Although one may suspect that when running complex operations the CPU would not have time to go idle, this is not the case. To illustrate this point, Intel used an example of DVD playback. Very stressful on the system as a whole, Intel's quick start technology allows the CPU to "hurry up" and perform the DVD decoding operations and then go idle until the frame is displayed to screen and the next scene needs to be calculated. This saves battery life because, although the system may require 3 watts or so to "hurry up", the power consumption goes down near .25 watts when idle. By averaging these two numbers, one can quickly see how quick start can extend battery life."”

The A8’s power consumption has to be well under that 3x max I quoted above, and the iPhone 3GS needs to be more than just 2x faster at executing instructions, but if possible then it’s quite feasible for the faster A8 to draw more instantaneous power but draw less power on average than the ARM11 core in the original iPhone.

Index The iPhone Becomes a Gaming Platform: Enter the PowerVR SGX
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  • jasaero - Friday, June 12, 2009 - link

    I am guessing Apple gets a better deal with Samsung as I think most of the flash in iPods was from them prior to iPhone. TI may make flash memory, but pretty sure they don't touch Samsung volume. From what I can gather also the Samsung ASIC and OMAP are pretty much the same anyhow or atleast have pretty close ARM/IM SoC matched lines. Reply
  • jasaero - Thursday, June 11, 2009 - link

    I am with you 100% on this. If you goto page 5 of these comments I linked to some good info on what is behind snapdragon and qualcomm's plans now that they own AMD/ATI handheld graphics IP. They also spent 100's of millions making their cortex core more powerful than the competition also. I am with you on Anand doing a more in depth look at the competing offerings here using his connections to get info tough to find for us. Its intersting stuff as this market is more IP oriented, but Qualcomm, intel and probably a lot of others add their own IP as they package these things in SoC's. Reply
  • iwodo - Friday, June 12, 2009 - link

    Yes I read it. On paper Qualcomm seems to have an edge on everything. ATI powered Graphics, Better then Cortex A8 design, and expertise in Mobile Wireless Chipset.

    However it doesn't seems any Manufacture are using their chips. From the charts Mainly Japaneses and Korean ( LG ) based phone maker. Given LG recently switched side to Non Qualcomm based to due to cost issues. We will see even less QualComm chip in Global Market since Japaneses Handset are not exported and unusable outside Japan.
    Reply
  • Barack Obama - Thursday, June 11, 2009 - link

    Was waiting to see what the fuss about Iphone 3G S was about. If I wasn't already tied down to a 2 year contract I'd buy one.

    Do you think Apple will gain dominance over the phone market as they seemingly are or other companies will get their feet in the door? Apple is looking at a Windows-like monopoly of the mobile phone market at the moment!
    Reply
  • anandtech02148 - Wednesday, June 10, 2009 - link

    these smartphones will eventually make PC, laptop, & netbook less rellevant, Apple already has 50,000 apps just for iphone, do they even have that much apps for their own macbook line?
    Intel,Amd & Nvidia is becoming a niche, with consoles and smartphone taking their customers away little by little.
    the only weakness to smartphone is how badly these cartel cellular operate. Get your acts together At&T and get aggressive broadband roll out.

    Reply
  • Mazik - Wednesday, June 10, 2009 - link

    "If Apple would just get their pre-ordering system working right I might not even have to camp out this year..."

    ...you can pre-order on att.com
    Reply
  • snookie - Wednesday, June 10, 2009 - link

    "Apple could be their own worst enemy with this faster hardware, and they have been seen to drop legacy support quite quickly already (Snow Leopard anyone?), things that other people can't get away with."

    Apple drop legacy support quite easily? No. You don't know anything about the history of Mac OS if you say that. Google Rosetta for one. Look at how long people are able to continue to install the latest Mac OS on old hardware for another. SL is a major rewrite of huge portions of the OS that Windows 7 could only dream about. It's the kind of rewrite that Microsoft doesn't have the skills, the will, or organization to do.

    "Palm has the Pre, it has faster hardware."

    Not anymore. Read the article.

    "The problem here is that either Apple developers are going to have to develop for the (s)lowest common denominator (20million units), and either risk annoying customers by making them unable to use the stuff/forcing them to upgrade, or making applications which aren't as impressive as they could be."

    Palm wishes they could have this "problem'". Palm has every little money in the bank and is in league with Sprint which is the most dubious cell company in existence right now. They make AT&T look good. They have terrible dev tools, have already pissed of a lot of developers, and you can only write web apps for the Pre. 8GB of ram and the terrible keyboard are showstoppers for me.
    Developing for iPhone or Pre is a quite easy decision. iPhone has the mass of the marketplace and a real SDK. Palm has neither and may never have.

    "While Leopard had nearly as shaky/buggy a start as Vista (though 99.9% of Mac users won't admit it), Leopard has reportedly morphed into a very stable and serviceable system."

    You must have dreamed this. Leopard had nowhere near the shaky start of Vista. I used both Leopard and Vista pre-beta and RC for many months. Its really amazing the things people say with no idea what they are talking about.

    "The greatest weakness of the iPhone is the controls."

    Why, because it doesn't have the kind of controls you are used to? Developers have done amazing things with multi-touch and the accelerometer.

    "The average phone user doesn't care much about games and game controls"

    I don't know what you consider average. Apple does in fact care about games and the iPhone and plenty of iPhone users buy them. Enough for a very robust marketplace. Check the numbers.

    I'm interested to hear about the radios and if we can expect better, stronger, clearer signals.
    Reply
  • michaely - Wednesday, June 10, 2009 - link

    2 cents? All you gave was a penny. I laughed at your post so much. Could you be anymore of a fanboy? You purposely go out of your way to diss Microsoft and Palm, but completely ignore the points you quoted. Snow Leopard is Intel only (READ: no G4/G5). Where is the support? You are talking about the past, we are in the present and looking to the future.

    The sad thing is you probably don't even own a iPhone. You are a sad excuse of a fanboy. PERIOD.
    Reply
  • jasaero - Wednesday, June 10, 2009 - link

    Anand,

    You hint ARM and Imagination Tech own the mobile procesing space here, but wondering if you have any write ups in the works that compare the PowerVR based intgrated GPU offerings to th also popular Qualcomm ATI based cores? Also in January Qualcomm purchased the ATI handheld unit and got rights to all related IP along with some staff to keep said mobile ATI core competitive.

    To me this could mean an advantage for qualcomm 's Snapdragon if PowerVR's cores aren't a lot better than Qualcomms ATI or PowerVR offering VERY affordable licencing? I know this goes outside the iPhone 3Gs review a bit, but it will have probably ALOT of snapdragon competitors soon! And some of these Snapdragon competitors could show up with even more mature Android.
    Reply
  • jasaero - Wednesday, June 10, 2009 - link

    Here is some good info on the unique ARMv7 ISA based Scorpion core used in snapdragon! I for the life of me can't find info on the ATI handheld core that Qualcomm uses and now owns?? They seem to have invested more in the ARMv7 ISA than their more or less standard Cortex competition. Of particular interest is the lower power and double width SIMD unit.

    Now who can find info on this ATI core?
    Reply

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