DMA37MD_WRITE
outb(DMA1_MODE, DMA37MD_AUTO|DMA37MD_WRITE|chan);
outb(DMA1_MODE, DMA37MD_SINGLE|DMA37MD_WRITE|chan);
outb(DMA2_MODE, DMA37MD_AUTO|DMA37MD_WRITE|(chan&3));
outb(DMA2_MODE, DMA37MD_SINGLE|DMA37MD_WRITE|(chan&3));