> I noticed also that Kim-Hoe Pang's ultra-DMA patch would turn on ultra
> DMA mode on any ultra-DMA drive, even on older chipsets that don't
> support it. That could be unpleasant.
>
The UDMA mode of an UDMA drive would NOT be enabled on a non-TX
chipset mobo. On power-up or after a hardware reset, the drive is in
normal PIO/DMA mode. To enable the UDMA mode in the drive, the host,
BIOS or OS, needs to send a SET FEATURE("enable UDMA mode
subcommand") AT command to the drive. A non-TX mobo will not send
this command to the drive.
UDMA mode is dis/enabled via BIOS setup. The patch does not
attempt to override user's BIOS setting.
To dis/en-able UDMA mode on the fly, my current thinking is to
have hdparm, with a new command line option, to
do it.
-kh