Maximum reference design for GT 650m meoery clock (GDDR3 or GDDR5) is 900MHz, that would give you effective clock of 1800MHz for GDDR3 and 3600MHz for GDDR5:
Of course individual laptop brand can go above or below the design. Usually, the GDDR5 version is clocked at 1000MHz and the GDDR3 version is at default 900MHz.
Maximum reference design for GT 650m meoery clock (GDDR3 or GDDR5) is 900MHz, that would give you effective clock of 1800MHz for GDDR3 and 3600MHz for GDDR5:
Of course individual laptop brand can go above or below the design. Usually, the GDDR5 version is clocked at 1000MHz and the GDDR3 version is at default 900MHz.