-=> On 29 Apr 96  15:58:19 Mike Bilow said to Udo van den Heuvel <=-

Hi Mike,

 MB> Udo van den Heuvel wrote in a message to Thomas Seeling:

 UvdH>> Where can I find info on how to use the DMA chips of my PC  
 UvdH> Or can I do polled I/O (180+K/s) and save the incoming data
 UvdH> to a (SCSI) HD without losing a bit?

 MB> Polled I/O is actually FASTER
 MB> than DMA through the motherboard controller, which is
 MB> non-bus-mastering DMA, 

PIO may be faster, but it requires CPU time, while MB DMA doesn't.
That is why SCSI disks are a BIG improvement on IDE in that you can rely
on the mouse cursor being viable all the time with SCSI (no clock).

 MB> provided that you don't pull an IRQ on every
 MB> byte or something similarly foolish as is needed with the serial port.

The serial port is not so bad if you have a FIFO.

 MB> But you can maintain data transfer at a pretty good clip using
 MB> IRQ-and-buffer techniques to do polled I/O with neither DMA nor even a
 MB> memory aperture, as the NE2000-style Ethernet card proves. 

ANd never mind the user interface :-(

 MB> If you need to hook an IRQ, do DMA, or meet critical time constraints,
 MB> then you will need a device driver under OS/2. 

That's what there there for.

Andrew

 
... Unable to locate coffee - Operator Halted
--- Blue Wave/Max v2.12 OS/2 [NR]