what is the effect of the cache memory on the direct memory access. is dma really affected by this or it has no effect on this at all.

plz tell me as soon as possible or recommend some sites
bye

I assume you're talking about the DMA controller built into CPU's? The CPU's internal address registers keep track of all cachable memory. This includes RAM and virtual memory. Modern CPU's have a 36-bit address bus & register, allowing them to keep track of 64GB total (notice that WindowsXP is based on 32-bit code and therefore can only keep track of 4GB of RAM, but has much more in total available virtual memory on the swap file).

The CPU's data cache contains data that is linked to addresses of system memory data, so that any changes made by the CPU to the cache is automatically made in RAM or the swap file on the next opportunity (the next FSB cycle). Also, any changes made by the OS or other devices to RAM or swap file data is also corrected in the CPU's cache on the next cycle. Because of this data cloning, and because the CPU's internal cache operates at core frequency, cache aids in CPU-side DMA by increasing CPU throughput.

Or in other words, cachable memory keeps the CPU cache fed, which keeps the CPU fed, which in turn allows the CPU to do more work per cycle.

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