Intel Confronts a Big Mobile Challenge: Native Compatibility

smaxp writes: "Intel has solved the problem of ARM-native incompatibility. But will developers bite? App developers now frequently bypass Android's Dalvik VM for some parts of their apps in favor of the faster native C language. According to Intel, two thirds of the top 2,000 apps in the Google Play Store use natively compiled C code, the same language in which Android, the Dalvik VM, and the Android libraries are mostly written.

The natively compiled apps run faster and more efficiently, but at the cost of compatibility. The compiled code is targeted to a particular processor core's instruction set. In the Android universe, this instruction set is almost always the ARM instruction set. This is a compatibility problem for Intel because its Atom mobile processors use its X86 instruction set."

Comments

Not useful to me, but I'll support Intel anyway.

[Dr. Manhattan]

I made an app for Android - ported an emulator written in C++. (Link in sig, if you're interested, but this isn't a slashvertisement.)

So the core of the app, the 'engine', is in C++ and must be natively compiled, while the UI and such is in Java. Naturally, the binary's compiled for ARM first. This actually runs on a lot of Intel Android tablets because they have ARM emulators. But, thanks to a user finally asking, I put in some time and now I can make an Intel version. (Heck, the original source was written for Intel anyway, so it wasn't a big stretch.) The existing tools are sufficient for my purposes. And it runs dramatically faster now on Intel.

However, for the developer it's mildly painful. The main issue is that you have a choice to make, with drawbacks no matter which way you go. You can include native libraries for multiple platforms, but that makes the APK larger - and according to a Google dev video I saw, users tend to uninstall larger apps first. In my case, it'd nearly double the size. So instead I'm putting together multiple APKs, so that ARM users get the ARM version and Intel users get the Intel version - but only Google Play supports that, not third-party app stores. I haven't looked into other app stores, and now it's less likely I will.

Note that native development can be important to apps for a non-technical reason: preventing piracy. An app written purely in Java is relatively easy to decompile and analyze, and pirates have a lot of techniques for removing or disabling licensing code. Adding a native component makes the app much harder to reverse-engineer, at least delaying the day that your app appears on pirate sites.

Re:Fsck x86

[OneAhead]

First of all, at this point, it is misguided to talk about x86 as an architecture; there is generally little or no architectural overlap between two x86 processors that are a few generation apart. x86 is an instruction set, or even more correct, a family of instruction sets. The distinction is important, especially in the age of complex instruction decoders; a lot of the more complex x86 instructions are internally decoded into smaller pieces, and one could say that the CPU internally runs its own, different instruction set. The fact of supporting a certain instruction set nowadays says almost nothing about the underlying architecture.

So we're talking about an instruction set. One that was conceived in an age where manual coding in machine language was far more common than it is today; the original x86 instruction set was designed to be easy for a human bitpusher to handle, whereas newer instruction sets like ARM are more geared to get the most out of a decent optimizing compiler. What followed for x86 was extension upon extension, and the instruction set is now so byzantine that x86 is a very difficult market to break into; the design complexity of the decoder can probably be overcome, but all the cross-licensing between Intel and AMD cannot. The complex, organically-grown instruction set also leads to some waste of silicon in having to support all those instructions, and waste of performance/energy efficiency in that the instruction set is not designed from the ground up towards efficiency. People on the x86 side make a compelling argument that this has become negligible, but the fact remains that I'm still not seeing any x86 processor getting (unbiased) performance/W scores that are close to common ARM processors.

My first computer contained a Z80, a true 8-bit processor (your claim that x86 has 8-bit mode is false; the lowest common denominator for x86 is the 16-bit 8086, which you're probably confusing with the 8-bit 8080 which is not x86 compatible). More relevantly, I also have experience running scientific workloads on a whole zoo of processors. I have particularly fond memories of the later Alphas, which wiped the floor with everything up until and including the Pentium 4, and were very competitive even against Athlon 64 and Core2 performance-wise (but not price-wise). Repeat after me: x86 has zero inherent architectural advantage!!! The big advantages it has is (1) economies of scale and (2) the higher profits of a mass market that generate more revenue to be pumped into R&D. There hasn't been a kid on the block that could compete on these fronts - not until ARM came around.

While Intel is sitting on an impressive pile of cash and R&D potential, their attempts to match ARM in performance/W are so far unsuccessful when looking at non-biased benchmark results, and ARM has profited from this in establishing a mass market of its own. Things are about to get interesting from here onwards. I can't predict whether x86 or ARM will win. The outcome might be coexistence, with x86 keeping its dominance in the server room, workstation, office and hard-core gaming, and everything else becoming ARM. Whatever the outcome might be, I am firmly rooting for ARM, though. Technically, it's leaner, more rationally designed instruction set that is more frugal with resources (die size, cache & memory usage) and better reflects present-day usage cases. And the fact that it's relatively straightforward for a newcomer to license it and start making chips will bring some healthy competition onto the stage.