This excerpt taken from the MRVL DEF 14A filed Sep 14, 2007.
Restricted Stock, Restricted Stock Units, Performance Units, and Performance Shares
A participant generally will not have taxable income at the time an Award of restricted stock, restricted stock units, performance units, or performance shares are granted. Instead, he or she will recognize ordinary income in the first taxable year in which his or her interest in the shares underlying the Award becomes either (i) freely transferable, or (ii) no longer subject to substantial risk of forfeiture. However, the recipient of a restricted stock Award may elect to recognize income at the time he or she receives the Award in an amount equal to the fair market value of the shares underlying the Award (less any cash paid for the shares) on the date the Award is granted.