The W83178S is a 13 outputs SDRAM clock buffer for 3-DIMMs models incorporate with W83196S14 which is the clock synthesizer especially for the 100 MHz models such as Intel BX chipsets. (Refer the datasheet fo Winbond W83196S-14) The W83178S receives the clock from chipset by the Buffer_In pin and provides almost zero-delay (less than 4 nS propagation delay) SDRAM buffer outputs for the 13 SDRAM clocks which are synchronous with the CPU clock outputs priovided by W83196S-14. The clock skew between any two clock outputs is less than 250 pS and the output buffer impedance is about 15 ohms. The W83178S also provides I2C serial bus interface to program the registers to enable or disable each SDRAM clock outputs.