When I select 300 MHz for my PowerPC on the ML507 board, the cross bar clock (CPMINTERCONNECTCLK) is also at 300 MHz.
Is this the correct setting?
No, the cross bar clock on the ML507 board can only run at 266 MHz. You will have to run the PowerPC at 400 MHz so that the tools will pick a 200 MHz cross bar clock or run the PowerPC at a lower frequency so as to not go out of specification for the cross bar clock.
This problem has been fixed in EDK 11.2, available at: