It is possible to copy at about 1.5MiB/s via DMA on the older spec boards.
We have found that trying to copy a 256k block of data will result in a system reset (watchdog timeout?). The DMA can copy 128k blocks without reset. It may be possible to get past this limitation using 68k interrupts but its doubtful. It appears while DMA is working the 68k has no access to the bus which limits its usefulness as its possible to copy at about 2MiB/s via 68k ASM using unrolled code 'MOVE.L (A0)+,(A1)+'. If you need fast data block copying keep away from DMA on older spec boards.
DMA on the CDZ is faster, exact speed not yet measured but this is the area the CDZ gets its faster loading times compared to the older models.