I am using the DMA of the PSoC 3 and I am interested to know the clock source of the DMA, does it depends on the IMO?
The clock for DMA transfers is BUS_CLK. (See also the DMA section in the PSoC3 technical reference manual). But this only affects multi-byte transfers. Otherwise, the rate of DMA requests determines the transfer speed (together with all the DMA setup time)