Hi, First of all I'm using linux-2.4.2. After various reboots and frustration I finally found out, why my machine did hang, as soon as I tried to burn a CD on my ATAPI CD Burner. Now I know why: A look at /proc/ide/hdc relveals that init_speed = 66 Which is wrong, because my CDBurner is only capable of Multiword2 DMA transfers (speed 34). Calling "hdparm -d1 -X34 /dev/hdc" fixes the problem. I even found these messages in /var/log/messages: Mar 14 18:01:48 pcrohloff kernel: hdc: set_drive_speed_status: status=0x51 { DriveReady SeekComplete Error } Mar 14 18:01:48 pcrohloff kernel: hdc: set_drive_speed_status: error=0x04 Which basically means that the linux driver even finds out that my drive doesn't like UDMA66, but doesn't react to it. I think that's a bug yes ? I got a PIIX chipset, so this might be a problem of this specific chipset driver (piix.c). Then again probably not ... so long Ingo Rohloff PS: Burning a CD was only one trigger for the problem. In fact accessing my CDBurner in any way (like mounting a CD, or reading from it) will lock up my whole computer, as long as "hdparm -d1 -X34" isn't called. It also doesn't depend on "ide-scsi" or "ide-cd" it will lock up with both modules. Also after unloading "ide-cd" and then reloading it, it is necessary to call "hdparm" again, because ide-cd will initialize the drive again with init_speed=66... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/