Will it benefit me to create another filegroup in addition to PRIMARY if I can't place it on a separate disk as PRIMARY and have only one CPU?

My understanding of file groups is the only benefit...if you can place a 'data' or user tables filegroup on a different disk, and the primary filegroup disk crashes you still have the 'data' on (hopefully) a good disk. Also if you have more than one CPU, multiple I/O tasks can read/write to more than one filegroup at a time.