Editorial: Why A Snapdragon S4 Galaxy S III Is Awesome
May 31, 2012 Conan Kudo
Yesterday, we found out the full specifications of the Galaxy S III for AT&T and T-Mobile USA. And many of you were disappointed that T-Mobiles version will have the dual-core Snapdragon S4 instead of the quad-core Exynos 4 SoC (system on a chip), even though the T-Mobile version will have 2GB of RAM instead of the 1GB amount in the international model. However, I see it as a good thing for us.
Obviously, having 2GB of RAM instead of 1GB of RAM means that Android can manage more in memory at once more quickly. What isnt often mentioned is that this benefit offers a performance increase that is greater than having more CPU cores, since the Dalvik VM can aggressively manage memory better than it can handle threading and delegating threads to multiple CPU cores. Plus, more CPU cores takes more power, which eats away at battery quite a bit. More RAM with a dual-core processor instead of less RAM and a quad-core processor will offer far greater benefits on a smartphone. As for the CPU type, let me explain why I am of the opinion that the Snapdragon S4 is better than the Exynos 4.
As many know, there are many different ARM chips used by device makers. Texas Instruments makes the OMAP series, Samsung makes the Exynos series, Qualcomm makes the Snapdragon series, ST-Ericsson makes the Nova and NovaThor series, and Apple makes the A series.
By and large, most of the CPU component of these chips are the same, with the exception of Qualcomm. OMAP 4, Exynos 4, Nova/NovaThor, and the A5/A5x are all ARM Cortex-A9 CPUs. That means that they are all virtually identical in performance. At one level or another, most people generally recognize this, which is why we focus so much on the GPU rather than the CPU in an SoC.
Lets focus purely on the CPU for the moment. Most ARM chipmakers have to use designs provided by ARM for the CPU cores. What the chipmakers get to decide is how the system chip is actually laid out and what interactions to optimize (I/O, caching, etc.). This means that there isnt a lot for most chipmakers to optimize beyond the interactions with the CPU and external components. NVIDIA takes this to the extreme with the Tegra architecture by making interactions between the CPU and the GPU extremely efficient for gaming.
Qualcomm is special because it has a license from ARM to develop its own CPU core technology based on ARM designs and instruction sets. Basically, it can cherry-pick the best features and optimize at every level. The result is that the Qualcomm Snapdragon of a particular generation will crush all competitors of that generation.
Snapdragon S2 and S3 use the Scorpion core, which takes some of the best features of both Cortex-A8 and Cortex-A9 ARM core designs and brings them into a single ARM core. Thats why the Scorpion core is very competitive to Exynos 3 (aka Hummingbird), OMAP 3, and other Cortex-A8 based SoCs. It also fared surprisingly well against many dual-core Cortex-A9 based SoCs like the Exynos 4 and the OMAP 4.
Snapdragon S4 uses the Krait core, which takes the best features of the Cortex-A9 and the Cortex-A15 ARM core designs with a much better manufacturing process to produce smaller chips that are far more power efficient and deliver amazing amounts of performance compared to its competitors (which are Cortex-A9 based). This is why dual-core Snapdragon S4 devices can go toe to toe with the quad-core Tegra 3 and Exynos 4 on the CPU front. At the same time, because of the massively improved power efficiency, CPUs using Krait cores will consume so much less power than Cortex-A9 CPUs that the amount of battery life improvement can be measured in several hours for active use and days for standby usage.
On the GPU side, the performance gap is a lot closer. The Adreno 225 is essentially the same GPU that was included in the Snapdragon S3 except with a few spec bumps and a doubling of the clock speed for the GPU cores. Though, a lot of bottlenecks were also eliminated in the new SoC arrangement in the Snapdragon S4. The result of this is that the performance of the Adreno 225 on a screen of 1024×600 resolution beats out all competitors except for the iPhone 4S performance wise (all competitors measured are pushing at lower resolutions, meaning the GPUs would perform much worse against the Adreno at the same resolution the Adreno is benched at). And even then, adjusting the Adreno 225 to push out at the same resolution as the iPhone 4S would make it surpass the GPU used in the iPhone 4S (the PowerVR SGX543MP2). With that in mind, I believe that the Adreno 225 is more than satisfactory for the Galaxy S III. Would I like a more powerful GPU? You bet. The Adreno 320 coming this fall to Snapdragon S4 is a total redesign for Adreno and is considerably more powerful, but I think nearly everyone will be fine with the performance the Galaxy S III will have with the Adreno 225.
If you dont believe me, you can check out the benchmarks yourself.
Of course, the Snapdragon S4 also includes an integrated modem onto the chip, which means that Wi-Fi, Bluetooth, FM radio, 2G GSM, HSPA+, and LTE are all controlled by a single chip. Having two chips as opposed to five or six chips (as required for several other solutions) means that even less power is required to actually use all these radios. Given how power-hungry radios can get, any form of reduction in power usage will be great. As of right now, only Qualcomms modem is certified for DC-HSPA (HSPA+42) on the T-Mobile network. Perhaps next year, ST-Ericssons Thor M7300 and M7400 modems will be validated for use on T-Mobiles HSPA+42 and upcoming LTE networks. When that happens, well see more diversity for SoCs on high end devices.
But if you are thinking that other carriers will get SoCs other than Qualcomms in the future, youd probably be wrong. Most LTE modems do not support U.S. Digital Dividend frequencies, which means the LTE networks of AT&T, Verizon Wireless, and most regional carriers will be stuck with Qualcomms modems. T-Mobile can use non-Qualcomm LTE modems because the AWS band T-Mobile is using is a standardized band that is well-supported. Verizon Wireless, Sprint, and most regional carriers operate CDMA2000 networks, which means they have no choice but to use Qualcomms modems, since no one else makes CDMA2000 modems because Qualcomm owns all the IP rights to the cdmaOne/CDMA2000 technologies. Maybe once CDMA2000/LTE carriers start offering devices that dont support CDMA2000, then well see non-Qualcomm Snapdragon LTE devices on those networks, provided that U.S. Digital Dividend, ESMR+Cellular 850, and Extended U.S. PCS bands are all supported by non-Qualcomm modems by then.
While it is technically possible to implement a multi-chip solution separating the system chip from the modem chip, it usually isnt worth it unless you have a specialized platform (or it is a tablet and you have the space to spare). Apple and Motorola take this route, but the cost is heavy. They lose quite a bit of internal space to having more chips to represent the SoC. It also worsens battery life as more chips must be powered by the battery. They only do it because of CDMA2000 support. Motorola does it with OMAP4, a 3G Qualcomm modem, and an in-house LTE radio chip. Apple does it with its in-house A-series chip and a Qualcomm modem.
For the foreseeable future, I think Qualcomms Snapdragon SoCs will dominate the non-Apple LTE device ecosystem. It will change over time as legacy technologies are phased out (in particular, CDMA2000) so that other modem chip makers can have their modems on the network, but for now, were going to have to deal with it. At least it is quite the enjoyable ride!
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