If you commit a probation violation, you subject yourself to being resentenced on the original charge. If the original charge carries a five year max, the maximum sentence on the probation violation would be that maximum sentence less time served.

If you're asking about consecutive versus concurrent sentencing, consecutive sentences are served back-to-back (1+1+1+1+1=5), and concurrent sentences are served together (five simultaneous 1 year periods = 1 year).