The first Beta version of Scientific Linux 6.3, a recompiled Red Hat Enterprise Linux put together by various labs and universities around the world, is now available for download and testing.
Scientific Linux 6.4 Beta 1 is a minor release and the development of the distribution is progressing smoothly. There are only two changes: sl-release-6.4-rolling has been updated and yum-conf-sl6x is now installed by default
According to the developers, you shouldn't expect a "yum" upgrade to SL 6.4 to work. A new install is the recommended method to move from "sl6rolling"(this alpha/beta release) and the released "SL 6.4."
More details about this release can be found in the official announcement. Download Scientific Linux 6.4 Beta 1 right now from Softpedia. Remember that this is a development release and it should NOT be installed on production machines. It is intended to be used for testing purposes only.