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The OpenBSD 4.9 release announcement says

"SMP kernels can now boot on machines with up to 64 cores;"

So OpenBSD does support several CPU's/cores?

If i have a Core2Duo cpu in my laptop (t7100) then would it bring greater performance if I use "SMP" kernel?

If this is true, then how can I install/use an SMP kernel under OpenBSD 4.9?

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up vote 8 down vote accepted

SMP has been supported since OpenBSD 3.6, released in 2004.

Presumably the old limit was 4 cores or 16 cores.

The easiest way to get SMP support is to install the bsd.mp kernel. That should happen by default if your system has multiple cores.

OpenBSD SMP project

As of June, 2004, SMP (Symmetric MultiProcessor) support has been merged into the main OpenBSD development branch. At this time, the i386, amd64, mvme88k, sparc64, macppc and hppa platforms support SMP.


Starting with OpenBSD 3.6, OpenBSD/i386 supports most SMP (Symmetrical MultiProcessor) systems. To support SMP operation, a separate SMP kernel (bsd.mp) is included with the installation file sets.

What OpenBSD systems support SMP?

A separate SMP kernel, "bsd.mp", is provided with the install file sets. If multiple processors are detected at install time, is automatically installed as the default boot kernel, /bsd, and the single processor kernel is renamed /bsd.sp.

See also:

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that's great news! thank you! – LanceBaynes May 2 '11 at 7:18

As an update to this question/answer, threading will become more useful in the 5.2 release, which will then supposedly make applications like mysql run faster.

If you are going to run the bsd.mp kernel for multiprocessor/multicore systems, even if it's NOT AMD, use the AMD64 platform instead of the i386 platform, as that seems to be the prevailing wisdom (from devs like Henning Brauer, re: bsdtalk interview with Peter Hansteen) on what runs 'better' on multicore systems right now.

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