The Qualcomm Snapdragon S4 (Krait) Preview Part II
by Anand Lal Shimpi on February 22, 2012 11:40 PM EST- Posted in
- Smartphones
- Snapdragon
- Qualcomm
- Krait
- Mobile
- Tegra 3
- Tablets
- NVIDIA
Final Words
As I mentioned at the start of this comparison, we're trying to compare two SoCs in two platforms that may offer wildly different experiences than shipping devices based on these SoCs. The hope (on both sides) is that we'll see similar, but likely slightly lower performance in phones. The reality will have to wait until we have final hardware in hand.
Qualcomm's strengths are clearly single/lightly threaded CPU performance as Krait is able to offer some significant steps forward in that department. Tegra 3 can hold onto an advantage in heavily threaded apps, but I'm not entirely convinced that in phones we'll see a lot of that.
The bigger question is about power efficiency, and this is the one not as easily answered based on what we know today. Qualcomm gains a lot by being on a 28nm LP process, however it also has more power hungry cores on that process. Device level power efficiency for a given workload may truly improve as a result of having faster cores on a lower power process (race to sleep, lower power idle). Generally speaking however, single threaded performance often comes at the expense of core level power efficiency. That's the reason it's taken this long for a 3-wide out-of-order core to make it into a smartphone. Will Moore's Law, and the 28nm LP process in particular, be enough to offset the power consumption of a higher performance Krait core under full load? Depending on how conservative device makers choose to build their power profiles we may get varying answers to this question.
Tegra 3 on the other hand should be a known quantity from a power consumption standpoint. All of the A9s in Tegra 3 are power gated (unlike in Tegra 2) and there's the fifth core for light workloads. For typical usage models I would expect better battery life out of Tegra 3 phones compared to Tegra 2 counterparts since the extra cores will likely be power gated, and idle power consumption should be lower. It's only for the heavier workloads where all cores are engaged that the impact of Tegra 3 remains to be seen.
There's also the LTE component. Today we're focused on the SoC comparisons however the first MSM8960 devices will also benefit from having integrated 28nm LTE baseband as well. Qualcomm will also have discrete 28nm LTE baseband solutions as well (e.g. MDM9615) for device makers who choose not to use Qualcomm application processors.
We'll obviously figure all of this out in due time, but my final concern remains with the device vendors. Far too often we review great platforms that are burdened with horrible software sold under the guise of differentiation. We're finally on the cusp of getting some really powerful smartphone hardware, I do hope the device vendors do these SoCs justice.
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Alaa - Thursday, February 23, 2012 - link
How about running more than one of these processes at once? Wouldn't 4 cores get more benefit?MonkeyPaw - Thursday, February 23, 2012 - link
The thing is, Tegra 3 is still on a single channel of memory. This was one of the design decisions that made me really question how valuable it was going to 4+1 cores. I think this is probably a very big reason it can't best Krait's 2 cores in any multi-threaded tests. I think they would have been better off going to a 2 core dual channel setup with improved graphics, and saved the move to quad core until Tegra 4.tipoo - Thursday, February 23, 2012 - link
The single channel memory was my first thought also. Four cores active at once plus a GPU all sharing one channel sounds like a terrible idea, that's probably a significant factor.piroroadkill - Thursday, February 23, 2012 - link
Your two cores crapped all over Tegra 3's 5.My god, Tegra 3 looks bloated compared to MSM8960.
I eagerly await devices of all types with this chipset! Bravo!
rahvin - Friday, February 24, 2012 - link
Just like Tegra and Tegra2 nVidia made design decisions to push paper specs over real performance and power savings. Personally other than a few token devices I expect Tegra3 to be a no show once Krait and Omap5 hit the scene.LetsGo - Thursday, February 23, 2012 - link
Looking at the number in the linpack benchmark I would expect the results to scale less than linearly, MDP MSM8960 = 107 MFLOPS single threaded, 218MFLOPS Multi- threaded!That chip has the smarts Impressive!
metafor - Thursday, February 23, 2012 - link
Since two cores share an L2 cache, it's very possible that one core's prefetch also feeds another. I don't think the Linpack program is very intelligent in this regard :/tipoo - Thursday, February 23, 2012 - link
The SGX 543MP2 in the iPad 2 pushes 148 in GLbench Pro offscreen. A year after its first début, why is no one else using it yet? I know the A5 die size is much larger than comparable SoCs because of it, but this here shows everyone else is focusing on CPU performance over GPU, and I think after a certain point the GPU will matter more for rich content.And the iPad 3 will be launching within months no doubt, some saying with a 543MP4 like the Vita has, which would make a large lead into an enormous one. Seriously, what's going on with everyone else?
Death666Angel - Thursday, February 23, 2012 - link
iOS unfortunately is pretty much alone in the mobile gamer department. Android is not really pushing mobile games as much. So big beefy GPUs are not that marketable. :-(Dribble - Thursday, February 23, 2012 - link
I always thought of tegra 3 as a stepping stone between last years standard of dual A9's @ 40nm to tomorrows standard of quad A15's @ 28nm.It looks like we have most of tomorrows chip today as we have a dual A15 equivalent @ 28nm. However is it really shipping soon - 28nm production isn't exactly where it needs to be yet for cheap mobile phone chips? Are the final released products going to be that far ahead of the 28nm A15's?