DMA on USB is not working?

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http://forums.fedoraforum.org – Hello. I have Fedora 17 (RussianFedora remix) installed on my laptop. When system reads/writes to usb-flash drive cpu is loaded on 100% (iowait). I think that's because it's uses PIO, not DMA. How to change it? It's great problem with live-USB for example (I tryed it on 3 PCs). Maybe I am mistaken and this is not DMA/PIO problem. I couldn't find solving of this problem (don't know what keywords to use). If it was already solved, please show me that thread. (HowTos)