The RAM frequency shows 400MHZ or 533MHZ in VAIO Control Center when the preinstalled RAM in TZ series is 667MHZ.
In the HW SPEC sheet, the original RAMM is written, NOT the performance capability of the RAMM.
Although the original RAMM is 667Mh, unfortunately TZ Series can perform maximum of 533Mh.
The ULV (Ultra Low Voltage) Processor's Host Clock is set up as 533MHz and CPU - Chipset's I/F (FSB) 533MHz.
Due to that Memory Bus Clock can not go over FSB、even though using 667MHz Memory, Memory Bus clock will be 533Mhz