hw.ata.ata_dma="0": can I do this during bootup at the loader prompt?

[Rob]

Hi,

In /boot/loader.conf, I have
   hw.ata.ata_dma="0"
to prevent a WRITE_DMA failure crash at bootup.
Unfortunately, this forces my UDMA100 harddisk to operate
at PIO4 speed.

There are patches flying around on this mailing list that might
solve the problem. I'm very keen on testing such patches, but I
should remove the line in loader.conf. However, if the patch does
not work, I end up with an unbootable disk.

It would be nice if I can set hw.ata.ata_dma="0" at the loader
prompt during bootup, so that the system at least will boot from
harddisk. Is that possible?

Thanks,
Rob.