Subject: Re: IDE summary, performance, config options?
To: None <>
From: Manuel Bouyer <>
List: current-users
Date: 02/02/2000 21:01:20
On Tue, Feb 01, 2000 at 05:15:27PM -0400, David Maxwell wrote:
> I've seen comments about other OS's IDE support along the lines of
> "We default to having all features turned off, for compatability, you have
> to turn them on and see which ones work on your hardware..."
> Could someone who knows, comment on NetBSD's defaults, and tweakable
> options? (And when to tweak them?)

NetBSD tries to guess what features are supported by the hardware and turn
them on by default, for hardware explicitely supported by the driver (mostly
relevant for pciide). The driver will fall back to safer settings is something
goes bad.
for pciide you can force the use of DMA for 'unknow' controllers by using the
flag 0x01. In this case the following is not relevant (the driver doesn't know
how to change modes). See pciide(4) for details.
pciide* at pci? dev ? function ? flags 0x0001
pciide* at pci? dev ? function ? flags 0x0000

For a controller supported by the pciide driver, foreach drive the driver
will use the higtest mode supported by both the drive and the controller.
It will fall back to a lower mode if too many errors occurs (the driver keeps
statistics about the errors/transfers ratio for this).
For each drive you can force the driver to use a specific mode (in this case
the fallback mechanism is disabled) by using a config flag. See wd(4) for
details; these flags also apply to ATAPI devices.
wd* at pciide? channel ? drive ? flags 0x0900
will force the driver to use Ultra-DMA 1; it will still use the default values
for DMA and PIO. Default:
wd* at pciide? channel ? drive ? flags 0x0000

Manuel Bouyer <>