Fwd: About the names of CPUs and architectures (original) (raw)

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Mon Jun 18 03:37:33 PDT 2012

I tried to send this a few days ago, but it seems like it never reached the list..? Weird; I'm trying to resend it. Sorry if it's a dupe.

*The background * Currently, there is a lot of different names floating around in the build system for the same piece of hardware, especially regarding Intel architecture. This is not just our fault, there is no complete world-wide industry consensus.

For the 32-bit Intel CPU, we have: x86, i386, i586 and ia32.

For the 64-bit Intel CPU, we have: x86_64, amd64 and x64.

Fredrik wanted to unite this as much as possible. Unfortunately, he did so by introducing new names that was not used before (ia32 and x64). Currently, these show up mainly in how the configurations are named (the directories under build/). While the new names might have their merits, I believe they are not as commonly used as the old names. I also believe not much is gained by introducing a new name.

As a reference, configure is consistently using the name x86_64 for the 64-bit Intel architecture, but switches between i386 and i586 depending on OS (and, of course, how antique the CPU is).

In the OpenJDK source code, the 64-bit architecture was previously relatively consistently named amd64, but recently this platform has been renamed x86_64 -- but only on macosx. This is an even more unfortunate situation, that we have different names internally for the same CPU depending on OS. We should really be able to avoid this.

The 32-bit architecture has been most commonly refered to as i586, but there is really no clear winner between i586 and i386.

On top of this is the difference between "cpu" and "cpu architecture", where the former specifices a specific cpu with a given address length (e.g. x86_64) and the latter a family of cpu:s with different address lengths (e.g. x86 and x86_64). Currently we support two such familys, the sparc family and the Intel family. In the current build-infra solution they are named "sparc" and "x86", respectively.

My proposal

I propose that we change our new default names to: 32-bit Intel: x86 64-bit Intel: x86_64 Intel arctitecture: x86

(As reference: 32-bit Sparc: sparc 64-bit Sparc: sparcv9 Sparc architecture: sparc)

Rationale: x86_64 seems like the easy choice. It matches the configure name, and the new macosx name. Appearantly it was important for macosx to change this, so we should try to move the rest of the product this was. It also matches other large open source projects like Linux. "amd64" seems a bit old-fashioned, and "x64" is more common in marketing than in development projects.

x86 is trickier. It is possible to argue for i586 instead, since it matches configure (sometimes) and the old name (sometimes). However, it feels like it is a superset of i386 and that it opens up for the possibility to be able to choose i386 instead, when that really is not an option. Also, I believe it would create a more coherent system of cpu and cpu architecture naming, corresponding to the sparc world (and possibly other future cpu architectures like arm (arch)/arm (32-bit)/arm64). I won't fight to defent this name, though, so if I'm voted down I'll accept that. :-)

Furthermore, I'd like to change the source so we use the new names as far as just possible. In the places where it is not possible (basically, where it will affect visible parts of the resulting product, like directory names or os.arch property), we should have a simple mapping table replacing the names that needs replacing.

Unfortunately, I'm leaving for vacation/parental leave today, and won't be able to implement any changes. Jonas and Erik might do that, but stated that there is "no promises".

But at least it would be good to hear your opinions. I hope we don't get as an infected debate as with the build/target issue; let's keep this one civilized ;-)

/Magnus

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