The NB3N1900K differential clock buffer is suitable for use in conjunction with a PCIe-compliant source clock synthesizer to provide point-to-point clocking for multiple agents. The device is capable of distributing reference clocks for Intel QuickPath Interconnect (Intel QPI & UPI), PCIe Gen1, Gen2, Gen3, Gen4. The NB3N1900K internal PLL supports 100 MHz and 133 MHz frequency operation. NB3N1900K supports HCSL output level.