[MPC8313]transfer data from PCI to DDR by DMA is very slowly

[Issac]

PCI of this chip is 66MHz@32bits.
Theoretically, it only needs 93us to transmit 24K bytes. 

Hower, It needs 930us to transmit 24K bytes.

I don't know what's wrong and how tu deal with it.

I I measured the waveforms of frame and irdy, as shown in the following figure.

Blue signal IRDY, green signal FRAME.