Due to a restriction in the Qsys Interconnect in the Quartus® II Software version 12.1sp1 and earlier only supports in-order transactions.
To maintain in-order transaction the Qsys interconnect will block pending transactions to different slaves by varifying the transaction addresses and de-asserting the ready signal until the current transaction completes.
To reduce transaction blocking, consolidate transactions to the same slave. If a Master sends transactions to the same slave the Qsys interconnect will accept the next transaction by asserting ready signal before the previous transaction completes, providing the slave can also accept next transaction.
This restriction is currently scheduled to be addressed in a future release of the Quartus II Software.