muticount -m is used to get or set the sector count for a device that supports multiple sector IO.
IO support -s is used to set the IO setting on a device. Most devices are set to use 16bit. By setting this to 1 it turns on 32bit IO for faster transfers of information.
Using_dma -a by default this is turned off. DMA or Direct Memory Access is way to control system memory without using the CPU.