Abstract: A multi reference phase locked loop (MPLL) generates a high speed clock frequency and phase locks it to a lowest common reference frequency derived from a selected one of at least two reference clocks. One of the reference clocks is a system reference clock in a FBDIMM system, another may be a forwarded clock in an AMB2. A prescaler reduces the frequency of at least the forwarded clock to the lowest common reference frequency which is the frequency of the system reference clock. A PLL at the core of the MPLL may be locked to the forwarded clock or the system reference clock for generating a high speed clock. A feedback divider generates the feedback clock for the PLL as well as other clocks required in the system. Furthermore, the MPLL provides a number of clocking modes, including modes to facilitate testing and powering down of sections of the circuitry for conserving power.

Abstract: A multi reference phase locked loop (MPLL) generates a high speed clock frequency and phase locks it to a lowest common reference frequency derived from a selected one of at least two reference clocks. One of the reference clocks is a system reference clock in a FBDIMM system, another may be a forwarded clock in an AMB2. A prescaler reduces the frequency of at least the forwarded clock to the lowest common reference frequency which is the frequency of the system reference clock. A PLL at the core of the MPLL may be locked to the forwarded clock or the system reference clock for generating a high speed clock. A feedback divider generates the feedback clock for the PLL as well as other clocks required in the system. Furthermore, the MPLL provides a number of clocking modes, including modes to facilitate testing and powering down of sections of the circuitry for conserving power.