Disk, 20 
  controller, 6 , 241 
  DMA, 246 
  DMA pointer registers, 246 
  drives, 6 
  external
    identification, 335 
    interface, 334 
    limitations, 335 
    pins, 334 
  external connector, 367 
    device ID, 370 
    pins, 367 
    signals, 368 
  floppy, 4 
  input stream synchronization register (DSKSYNC), 250 
  internal - pins, 336 ,power, 336 
  interrupts, 220 , 250 
  MFM Encoding, 250 
  read data register, 248 
  write, 246