For the Romley/Grantley platform, there are three different clocks that are needed. For each type of clock, there is a specification called the Intel Yellow Cover spec. Renesas will always have a solution that follows the Yellow Cover specification. In the case of Romley/Grantley, the main clock that follows the CK420BQ specification is the 932SQ420D. For some platforms, all outputs may not be necessary, so a reduced pin-out device can be used. For these cases, Renesas also has alternatives. The same goes for the buffers and peripheral clocks that are needed for Romley/Grantley. The alternate devices meet the performance specifications that are set by Intel in the Yellow Cover specification.