The Qualcomm Snapdragon S4 (Krait) Preview Part IIby Anand Lal Shimpi on February 22, 2012 11:40 PM EST
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.