I've made a patch adds timecounters to the alpha port.
To use it on -current:

cd /usr/src/sys/arch
ftp -a -o - http://www.netilium.org/~tnn/alpha-timecounters.diff.txt | patch

... and recompile your kernel.

Beware, options COMPAT_OSF1 is currently not supported.
See also:
http://mail-index.netbsd.org/tech-toolchain/2006/08/20/0000.html

Tested on MP. Suggestions for improvement are welcome.

Have fun,
-Tobias