Virtualized DU function on x86-based server b) Virtualized DU function on x86-based server with multiple timing NICs Figure 10-36 Virtualized DU Server Architecture Additional ASIC-based hardware acceleration cards are also used SO that the intensive baseband processing can be offloaded from the primary CPU complex. Other PCIe slots are used to provide additional capabilities using peripheral or auxiliary cards. NIC cards with timing support, or time sync NICs, are essential to maintain the timing accuracy on the DU server platform because the x86 cannot do it unassisted. It is the time sync NIC that provides the hardware to support the T-GM, T-BC and T-TSC clocks for the PTP telecom profiles at high accuracy. An important point to understand-for high-accuracy timing-is that the x86 platform itself is not (and should not be) the PTP clock in the path of the timing between the DU and RUs but will nor- mally recover its timing from the PTP hardware clock (PHC) on the NIC card. The x86 uses a Linux package, ptp41, to accurately synchronize the time on the NIC card with the remote T-GM. The ptp41 process handles PTP traffic on the NIC port, updates the NIC PHC, and tracks the syn- chronization status. The x86 can also run the phc2sys process to update the system real-time clock from the PHC in the NIC card (the PHC is aligned to a remote grandmaster using PTP). The NIC card is the source and distributor of accurate PTP time for the x86 server and other devices in the network. The x86 server does not have the hardware capability to align its system real-time clock with the PHC on the NIC card to a high degree of accuracy. For this reason, in the case where an x86 server has multiple NIC cards, the server cannot distribute time accurately to the multiple NIC cards from the system real-time clock. Each NIC card has its own PHC, and the server cannot accurately (at the level required for mobile) transfer time between the cards. The NIC cards must be daisy chained together externally and some mechanism used to distribute 