OK, the Mediator 1200 models can do DMA between cards (which is why TV cards work, for example), but they can't DMA to fastmem.
This is because the Mediator doesn't include an accelerator but is designed to wedge between the A1200 and an existing accelerator.
Fast memory on most A1200 accelerators is simply RAM that is attached to the processor. Nothing on the A1200 side of the bus can see it. The only devices that can read or write that memory have to be ON the accelerator.
Being wedged between the A1200 and the accelerator, the mediator simply doesn't have access to the memory on the accelerator. There is absolutely nothing it could do to read or write the accelerator fastmem. The CPU is the only thing that can see both the mediator and its fastmem, so to get data off of a PCI card and into memory, the CPU has to read it from the card and write it into memory.
Technically, the mediator could read and write chip memory, but that would be useless; its just too slow to be worth while, and also, most accelerators aren't design to expect any other devices on the a1200 expansion port to be reading or writing chipmem through it, so you could have problems there.
