Frequently Asked Questions for FreeBSD 6.`X`, 7.`X` and 8.`X`
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# 4.3 Architectures and Processors

4.3.1. Does FreeBSD support architectures other than the x86?
4.3.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?

4.3.1. Does FreeBSD support architectures other than the x86?

Yes. FreeBSD currently runs on the Intel x86 and the AMD64 architectures. The Intel EM64T, IA-64, ARM®, PowerPC®, sun4v and SPARC64® architectures are also supported. Upcoming platforms are MIPS® and S/390®, join the FreeBSD MIPS porting mailing list for more information about ongoing work on the MIPS platform. For general discussion on new architectures, join the FreeBSD non-Intel platforms porting mailing list.

If your machine has a different architecture and you need something right now, we suggest you look at NetBSD or OpenBSD.

4.3.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?

Symmetric multi-processor (SMP) systems are generally supported by FreeBSD, although in some cases, BIOS or motherboard bugs may generate some problems. Perusing the FreeBSD symmetric multiprocessing mailing list may yield some clues.

FreeBSD will take advantage of HyperThreading (HTT) support on Intel CPUs that support this feature. A kernel with the `options SMP` feature enabled will automatically detect the additional logical processors. The default FreeBSD scheduler treats the logical processors the same as additional physical processors; in other words, no attempt is made to optimize scheduling decisions given the shared resources between logical processors within the same CPU. Because this naive scheduling can result in suboptimal performance, under certain circumstances it may be useful to disable the logical processors with the `machdep.hlt_logical_cpus` sysctl variable. It is also possible to halt any CPU in the idle loop with the `machdep.hlt_cpus` sysctl variable. The smp(4) manual page has more details.

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