> > when I send a SCSI packet command to one of them (any packet command
> > eg. an eject tray request) the SCSI bus will stall for a moment,
> > causing all targets on the SCSI bus will get out of sync.
>
> I'm not sure what you mean by this.

the bus locks up for a moment. (eg. If the other drive is reading a CD,
itt will stop reading for a moment. If the other drive is writing a CD,
the cdrecord process will say ``out of data'', and the disc will be wrong
of course.)

> Sounds to me like disconnect/reconnect isn't enabled for those targets.
> This an i386 system so you can check in the BIOS?

disconnect/reconnect is enabled.

now I have everything in async mode, and it looks okay, but I still have
two questions:

- why does it work with some PLEXTOR drives in sync mode
  maybe hardware difference? anyone with the same experiences?
- why does it work with FreeBSD in sync mode?