Hi,

I have a crappy hard disk and am trying to back up stuff from it onto my newer hopefully less crappy disk. There are dead sectors on the disk and some files can't be read (at all) so OpenBSD downgrades the transfer mode down until PIO mode 4. I noticed the transfer speed slowing down extremely, and I would guess it's due to these downgrades, which are done when reading certain blocks continuously produces errors. But there are files on the disk that ARE READABLE and I don't want to reboot every time I end up on a trashed area on the disk, since the rest is fine and can be read in Ultra-DMA mode 5.

I looked it up a bit, and found out that apparently you can change device flags - including the transfer modes - with the config/UKC (User Kernel Config) utility, but AFAIK that is for rewriting the kernel image without recompiling. When OpenBSD downgrades the DMA modes, it's obviously doing something else, and I just need to do the reverse operation. The point being: if it can be downgraded without booting, it can be changed, and therefore upgraded without booting.

Anyone know how to upgrade from PIO4 without a reboot?