Solution:

PPC-123T/PPC-153T use PCM-9571 version A1 board only can support Celeron CPU. As to supported Celeron, they should be PGA(CPU speed below 500Mhz) or FC-PGA (CPU speed up to 600 Mhz) type. However, FC-PGA type CPU must be "B" stepping (Vcore 1.5V) not "C" stepping (Vcore 1.7v). It means the CPU information displayed on its surface should have SL3W7 or SL3W8. For detailed Celeron CPU specification, please check out the attachment. Rev. B1 can support CPU higher than 850MHz.