From: google@holzapfel.biz   
      
   Imagine you're your favorite mid- to late-90's busmaster capable MCA adapter,   
   let's say a network card.   
   You have one single DMA level configured in your POS. It's yours.   
   You are on a Type 2 planar (late SCB DMA instead of 16-bit PIO) or more, and   
   you earn your money by writing data from the system memory onto the bus (TX),   
   and also at random times from the bus into system memory (RX).   
      
   You want to transfer data now.   
   You knock on the PREEMPT# line, arbitrate, and then you win!   
   What do you do to actually transfer the data?   
      
   a) Do you fire an interrupt, wait for the CPU to pick it up, configure the   
   system DMA controller to do the work?   
   b) Do you, as a smart-ass busmaster card, instruct the DMA controller to do   
   the work for you?   
   c) Anything else?   
      
   And finally, does it matter which direction the data is going?   
   Like for RX it's the adapter to initiate the DMA transfer, and for TX it's the   
   CPU? Or is it all the same?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)