shutdown does not power down

[Unga]

Hi

I'm using RELENG_7 on i386.

I noticed recently that "shutdown -p now" does not switch off the computer.

I'm trying to understand how does the /sbin/shutdown performs a power down. I had a detailed look at the source code involved but find it difficult to see how.

The program flow seems to be is as follows:
shutdown => [/sbin/init or /sbin/halt] => reboot() => boot() => shutdown_final => shutdown_halt() => cpu_halt()

Could you guys help me to identify how does shutdown request a power down.

Many thanks in advance.

Unga