TIP: Disable APM with SMP

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TIP: Disable APM with SMP

Posted by Jason on Wednesday April 03, @11:13AM
from the dept.
If you are planning on building a multi-processor system, you will need to turn off Auto Power Management to prevent the system from hanging and generally being cantankerous.

In December, I built an SMP (Symmetric Multi-Processor) system to be used as my wife's main workstation. However, I had only one processor (PIII 1GIG) on the ASUS mobo at the time it was installed. Since that time we have been using Auto Power Management to automatically suspend the system during times of inactivity.

After adding the second processor and compiling an SMP kernel, I started having problems almost immediately. The system would hang and generate strange and unhappy tones. It also locked up during a buildworld- not what I wanted from my new dual PIII system.

I suspected APM was causing the problem because the system would act like it was suspending, but the screen would not go blank. The /var/log/messages file also indicated a suspend and wake had occurred. But shortly after that- lockup! I decided to post my suspicions to the comp.unix.bsd.freebsd.misc newsgroup. They were immediately confirmed and apparently it's an Intel/SMP thing, and you cannot have APM enabled for ANY operating system using SMP.

After disabling APM in the kernel and System BIOS the problem went away. Now I can do a make buildworld on FreeBSD-4.5-RELEASE in just under 28 minutes!

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