Red Hat has announced the availability of RHEL 5.8. You can find more information on this here:
From a mainframe perspective this has been a pure bug fix release. There is one important feature update though. Red Hat included an update to the additional
gcc44 package enabling complete z196 support. As a dependency the
binutils220 package will be installed as well. With those two packages you can start building binaries targeted for the z196 with the
-march=z196 option or at least tune for it with options like -
march=z9-109 -mtune=z196.