Knowledge Base

Hardware

Does PC-BSD support SMP (dual processor)?

Tags: -

Related entries:

• After setting up PC-BSD on a dual-booted box, a boot screen never appears, instead the system restarts itself.
• I want to install PC-BSD to dual-boot computer already using GAG as a boot-manager. How do I configure GAG to boot PC-BSD?
• I have a dual intel 700 mhz system (AMI BIOS), I have at times had FreeBSD (up to and including 5.3) with no installation issues whatsoever. I have successfully loaded PC-BSD on older machines, but when I try to load it on this one, I get the desktop, then about 15 seconds later it reboots. Any info you could providew would be greatly appreciated, as this box is my primary.
• I have a PowerBook G4 can PC-BSD be installed on it?
• I have a dual-core/dual-cpu pc is it supported?

20745/61%Last update: 2007-09-28 22:59
Author: Charles-André Landemaine
Revision: 1.5

You can comment this FAQ

Comment of Andrei Kolu:
Yes. SMP was enabled by default in the GENERIC kernel as of FreeBSD 5.2.

The intention was also to enable it by default for the FreeBSD 5.3 release, but problems running the SMP kernel on certain UP machines led to the decision to disable it until those problems can be addressed. This is a priority for FreeBSD 5.4.

In FreeBSD 4.X, SMP is not enabled in the default kernel, so you must recompile your kernel to enable SMP. Take a look at /sys/i386/conf/LINT to learn which options to put in your kernel config file.

http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/compatibility-processors.html
Added at: 2038-01-19 04:14

Comment of Sascha Dorff:
FreeBSD 6.0 isn't compiled with SMP support by default.
In 6.1 they ship with a separate SMP Kernel. You can change your default kernel after installation in the systemadministration. But PC-BSD install an non-SMP kernel by default.
Added at: 2038-01-19 04:14

Comment of Jerry West:
There is (was) also a bug which meant the OS ignored the second and subsequent (virtual) CPUs in a multi-core processor. See http://www.freebsd.org/cgi/query-pr.cgi?pr=96203
for details.

PC-BSD seems to still ignore virtual cores as of FreeBSD 6.1-RELEASE-p2 (PCBSDv1.2-SMP) #2: Thu Jul 6 11:02:36 PDT 2006.

The bug report gives a workaround (not tested extensively but it seems to work): set machdep.hyperthreading_allowed=1
using sysctl(8) and/or in /etc/sysctl.conf

The bug report claims the issue was fixed in 6.1-RELEASE, so I don't understand why PC-BSD still displays the old behaviour.
Added at: 2038-01-19 04:14