Several different kernel-rt


I am just curious of what the difference between kernel-rt, kernel-rt-timing and kernel-rt-trace is? I was looking for real time kernels with sources for 11.0 and found those in the build repo of sdietrich: Index of /repositories/home:/sdietrich:/Kernel-RT/openSUSE_11.0/i586.
I am just familiar with the plain kernel-rt and it would be nice if someone would enlighten me of the features of the other two.