The affinity64 mask binds processors to specific threads, similar to the affinity mask option. Use affinity mask to bind the first 32 processors, and use affinity64 mask to bind the remaining processors on the computer. This option is only visible on the 64-bit version of SQL Server.
This feature will be removed in the next version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. Use ALTER SERVER CONFIGURATION (Transact-SQL) instead.