The SuperDisk you have inserted is not an internal RAM disk. This behavior is an anomaly under Apple System Profiler 2.1.1. It may also occur with other third-party removable-media solutions connected to iMac via the USB port. This anomaly has been corrected in Apple System Profiler 2.1.2, which is available for download from Apple Software Updates sites.
These articles can help you locate the software update mentioned here: