In People v. Rosbury (1997) 15 Cal.4th 206, the defendant was on probation for a robbery when he was convicted of an attempted second- degree robbery. His probation was revoked at the same time that he was sentenced for his second crime. ( Id. at p. 209.) The court held that probation was not tantamount to serving a sentence as that phrase is used in section 667, subdivision (c)(8). The court further held that the defendant "did not begin to serve his sentence before he was committed to the sheriff's custody . . . ." ( Id. at p. 211.)