This Answer Record describes improvements that were made to the PLB Ethernet Core in EDK 6.1 Service Pack 2.
In EDK 6.1 SP2, timing improvements made to the PLB 10/100 Ethernet MAC core allow it to meet a 100 MHz timing requirement on the PLB.
Additionally, Level 0 driver support was added for the PLB 10/100 EMAC (software version v1.00.d).
These fixed are contained in the latest 6.1 EDK Service Pack, available at:
The first service pack containing the fix is EDK 6.1 Service Pack 2.