Are you using the SCC Data Center? If you are, note that the MCPC is a multi-user Linux, specifically Ubuntu 10.04.x. The SCC cores themselves are intended to be single-user.
If your research group has several users logged into the MCPC, each user can edit and build without affecting SCC usage. Currently, it is the responsibility of your research group to schedule single-user access to the SCC cores. We are looking into some software tools that will aid you in doing this.
SCC operation is not virtualized. When you load a program on the SCC cores, you are running on the actual SCC hardware.