To stop CPU throttling from affecting jackd and other apps you can change the cpufreq priority:
/etc/rc.d/rc.cpufreq performance
This can be reset by
/etc/rc.d/rc.cpufreq ondemand
A carefully crafted ~/.asoundrc may be needed in some cases.
Guides on using an alsa only application through JACK:
Using ccache can speed up rebuilds a lot. When set up, it caches the binary objects as applications are built, and later it copies those objects back, instead of having to recompile them.
Slackware comes with ccache.
To start using it, get root and:
cd /usr/local/bin ln -s /usr/bin/ccache cc ln -s /usr/bin/ccache c++ ln -s /usr/bin/ccache gcc ln -s /usr/bin/ccache g++
To set a max size for the cache:
ccache -M 5G
That sets a max size of 5GB in /root/.ccache
You obviously need to set it for your needs and available space.
To see some info about ccache, do:
ccache -s
To temporarily turn it off:
export CCACHE_DISABLE=1
If that fails to work then just move the symlinks out of /usr/local/bin
Don't forget to read the man page.