0401-04D6 ---- used by EISA systems only


0401   r/w DMA channel 0 word count byte 2 (high)
0403   r/w DMA channel 1 word count byte 2 (high)
0405   r/w DMA channel 2 word count byte 2 (high)
0407   r/w DMA channel 3 word count byte 2 (high)

040A   w   extended DMA chaining mode register, channels 0-3
        bit 7-5      reserved
        bit 4   = 0  generates IRQ13
            = 1  generates terminal count
        bit 3   = 0  do not start chaining
            = 1  programming complete
        bit 2   = 0  disable buffer chaining mode (default)
            = 1  enable buffer chaining mode
        bit 1-0      DMA channel select

040A   r   channel interrupt (IRQ13) status register
        bit 7-5  interrupt on channels 7-5
        bit 4    reserved
        bit 3-0  interrupt on channels 3-0

040B   w   DMA extended mode register for channels 3-0.
       bit settings same as 04D6
        bit 7   = 0  enable stop register
        bit 6   = 0  terminal count is an output for this channel
(default)
        bit 5-4      DMA cycle timing
            = 00 ISA-compatible (default)
            = 01 type A timing mode
            = 10 type B timing mode
            = 11 burst DMA mode
        bit 3-2      Address mode
            = 00 8-bit I/O, count by bytes (default)
            = 01 16-bit I/O, count by words, address shifted
            = 10 32-bit I/O, count by bytes
            = 11 16-bit I/O, count by bytes
        bit 1-0      DMA channel select