We are planning on purchasing some IDE hard drives which
support the relatively new Ultra ATA 33MB/sec mode.  Our
motherboards, BIOS, and disks support it, but does NetBSD?  A
quick look through wdc.c shows that wdcattach can deal with drq
parameters, but none of the sample configs for i386 have a wdc
configured for DMA.  Yes, I'm clueless when it comes to DMA
and/or hard drive controllers.  :)

  On a related note, I notice that the wdp_piotiming data
returned during wdopen or wdattach doesn't seem to be used
anywhere.  What PIO mode(s) is NetBSD capable of doing?  Is it
entirely decided by the controller and hard drive?  Further
cluelessness on my part, I know...  :)  (At the hardware level,
does a controller simply extend the ISA/PCI bus cycles for the
desired length for the various PIO modes via IORDY etc.?  If so,
wouldn't the performance and the appropriate PIO mode depend on
what the ISA bus was running at?  I believe my machine at home
allows one to vary the ISA bus speed over a range, so an 8MHz bus
PIO mode 4 corresponds to a 12MHz bus PIO mode 3, i.e. a Mode 4
capable device at 8MHz may not handle Mode 4 at higher speeds.)

  Thanks in advance for info.

  Brian
-- 
Brian Grayson (bgrayson@ece.utexas.edu)
Graduate Student, Electrical and Computer Engineering
The University of Texas at Austin
Office:  ENS 406       (512) 471-8011
Finger bgrayson@orac.ece.utexas.edu for PGP key.