This is an in-depth analysis of the current capabilities and performance of the mobile phone platform.
1) The mobile platform is much, much slower than the desktop.
2) This is unlikely to change in the immediate future.
Here’s the core section about the hardware side of mobile development:
The hardware angle
But a factor of 5 is okay on x86, because x86 is ten times faster than ARM just to start with. You have a lot of headroom. The solution is obviously just to make ARM 10x faster, so it is competitive with x86, and then we can get desktop JS performance without doing any work!
Whether or not this works out kind of hinges on your faith in Moore’s Law in the face of trying to power a chip on a 3-ounce battery. I am not a hardware engineer, but I once worked for a major semiconductor company, and the people there tell me that these days performance is mostly a function of your process (e.g., the thing they measure in “nanometers”). The iPhone 5′s impressive performance is due in no small part to a process shrink from 45nm to 32nm — a reduction of about a third. But to do it again, Apple would have to shrink to a 22nm process.
Just for reference, Intel’s Bay Trail–the x86 Atom version of 22nm–doesn’t currently exist. And Intel had to invent a whole new kind of transistor since the ordinary kind doesn’t work at 22nm scale. Think they’ll license it to ARM? Think again. There are only a handful of 22nm fabs that people are even seriously thinking about building in the world, and most of them are controlled by Intel.
In fact, ARM seems on track to do a 28nm process shrink in the next year or so (watch the A7), and meanwhile Intel is on track to do 22nm and maybe even 20nm just a little further out. On purely a hardware level, it seems much more likely to me that an x86 chip with x86-class performance will be put in a smartphone long before an ARM chip with x86-class performance can be shrunk.
Update from an ex-Intel engineer who e-mailed me:
I’m an ex-Intel engineer, worked on the mobile microprocessor line and later on the Atoms. For what it’s worth, my incredibly biased opinion is that it’s going to be easier for x86 to get into a phone envelope with the “feature toolbox” from the larger cores than it will be for ARM to grow up to x86 performance levels designing such features from scratch.
Update from a robotics engineer who e-mailed me:
You are perfectly right that these will not bring ultra major performance boost and that Intel may have a higher performing mobile CPU a few years from now. In fact, mobile CPUs is currently hitting the same type of limit that desktop CPUs hit when they reached ~3GHz : Increasing clock speed further is not feasible without increasing power a lot, same will be true for next process nodes although they should be able to increase IPC a bit (10-20% maybe). When they faced that limit, desktop CPUs started to become dual and quad cores, but mobile SoC are already dual and quad so there is no easy boost.
So Moore’s Law might be right after all, but it is right in a way that would require the entire mobile ecosystem to transition to x86. It’s not entirely impossible–it’s been done once before. But it was done at a time when yearly sales were around a million units, and now they are selling 62 million per quarter. It was done with an off-the-shelf virtualization environment that could emulate the old architecture at about 60% speed, meanwhile the performance of today’s hypothetical research virtualization systems for optimized (O3) ARM code are closer to 27%.
I’m afraid my knowledge of the hardware side runs out here. What I can tell you is this: if you want to believe that ARM will close the gap with x86 in the next 5 years, the first step is to find somebody who works on ARM or x86 (e.g., the sort of person who would actually know) to agree with you. I have consulted many such qualified engineers for this article, and they have all declined to take the position on record. This suggests to me that the position is not any good.
If software is your thing, this should cause you some concern. I’ve always understood that Moore’s Law would run out of gas some day, but it seems that those days are upon us. It seems like the days of software development coasting along on bloated code made possible by exponential improvements in processing speed are coming to an end.