On 2 Oct 99, at 2:49, [log in to unmask] wrote:

> The typical mother board has two IDE channels with two devices
> allowed on each channel, usually referred to as primary and
> secondary (or sometimes master and slave).

  When dealing with IDE/EIDE/ATAPI, "master" and "slave" typically
refer to the two devices on a channel, not the two channels on a
controller....

> The question is: when attaching only one device to a channel, is it
> necessary to attach it to the primary (or master) connection? Or is
> it possible to leave that empty and attach one device (such as a
> CD-ROM drive) to the secondary (slave) connection only?

  Generally, whether a device is master or slave on its channel
depends on how its jumpers are set -- the connectors on the cable are
identical.
  [There is an exception:  If your cable has a "twist" between two of
the connectors, you can jumper both devices as "cable select".]

  I've seen enough machines with CD-ROM drives jumpered as "slave"
without a master device on the channel to know that this
configuration works, but I suspect that hard drives may not be so
accomodating.  [(1) Hard drives can be auto-detected in CMOS setup;
other kinds of devices generally are not.  (2) Some brands/models of
hard drives have difficulty when configured as slave to some other
brand/model as master; this implies that a slave hard drive may rely
on the master's controller for some functions.]  I have not actually
performed this experiment.

David G

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