On Tue, 9 Feb 1999, Hugo Bouckaert wrote:
>But can anyone tell me what this
>master /slave designation means and why you can, for example, have a hdd
>disk without having a hdb disk (I came across this recently)?
I, personally, have an HDD disk without having an HDB disk. This rumour,
therefore, however you discovered it, is not true. The only configuration which
I have never been able to get working is to have a slave disk without its
corresponding master disk.
The IDE protocol is a way of operating up to 4 disks in up to 2 sets of 2.
There are, on other than quite old motherboards, 2 IDE connectors, one for the
primary disks and the other for the secondary disks. These two sets of disks
work essentially identically, except that they use different IRQs. Older
motherboards often just have 1 IDE connector, i.e. for the primary disks.
Each IDE cable can be connected to either 1 or 2 disks. If you connect it to 1
disk, then that disk must be configured as the master. If you connect it to 2
disks, then one must be configured as the master and the other as the slave.
These terms have meanings within the IDE protocol, but, unless you're really
into the ugly low-level details, there's no need to care. N.B.: Some very old
disks have a special setting, which is neither master nor slave, which must be
used if that's the only disk which you wish to connect to an IDE cablek
Many IDE disks, in addition to the master and slave settings, offer a "cable
select" setting. The purpose of this setting is to automate things a bit by, in
theory, relieving you of the need to care about master and slave disks. You can
simply set both disks to "cable select", and then let IDE decide which is
which. The problem, of course, is that you still really need to know which is
which anyway as the difference is still significant from the operating system's
perspective: DOS always allocates the lower letter to the master disk, Linux
uses specific device sets for each type of IDE disk, etc.
Linux uses the hda devices for the primary master disk, hdb for the primary
slave, hdc for the secondary master, and hdd for the secondary slave. You
observed that hdc tends to be the CD-ROM, but that's simply because most people
connect their CD-ROM, if it's IDE, as the secondary master.
You observed that LILO needed to be on hda, i.e. the primary master disk. While
DOS-based systems will only boot if they're installed on the primary master
disk, I do not believe that LILO is quite that restrictive. My personal
experience, and perhaps I'm just ignorant of some lilo.conf directive, is that
LILO can be installed on either primary disk, and suspect that the only reason
that it won't work when installed on a secondary disk is that it doesn't (yet)
recognize the other IDE IRQ. If anyone knows how to get LILO to work from hdc
or hdd, I'd sure appreciate the hint.
--
Dave Mielke | 856 Grenon Avenue | I believe that the Bible is the
Phone: 1-613-726-0014 | Ottawa, Ontario | Word of God. Please contact me
EMail: [EMAIL PROTECTED] | Canada K2B 6G3 | if you're concerned about Hell.
