Re: Does Adding a 2nd IDE Hard Drive (Master/Slave setup) Slow Down Both Drives?

"Thomas G. Marshall" wrote:
Timothy Daniels said something like:
The drivess are still treated by the controller and the BIOS
as if they were jumpered as Master/Slave when using
Cable Select. I think you meant to say that Dell relies
on Cable Select and not jumpers to set the Master/Slave
differentiation between the drives.

[.......]
Does the ATA chipset even give a crap? The point being: the
system is expecting for a primary at the end of the cable, and
a slave further inward (?). The CS business is only to tell the
drive itself how to configure.


The IDE channel controler has no way to know which drive
it's talking to or hearing from on the same channel unless
the drives indicate whether they are One or the Other.
The names given by the industry (unfortunately) for One
is "Master", and for the Other it gave the name "Slave".
The connotation between "Master" and "Slave" may have
made sense at one time, but not in the past 10 years or so.
The only difference between "Master" and "Slave" now has
to do with the *default* HD boot order given by the BIOS.
That HD boot order has the "Master" on IDE channel 0 at
its head - and thus the HD whose MBR gets control at
boot time. But if there is no "Master" HD on channel 0, the
MBR of the "Slave" HD on channel 0 will get control. If there
is no "Master" or "Slave" on channel 0, the BIOS puts the
"Master" on channel 1 at the head of the HD boot order.
If there is no "Master" there, either, the BIOS will give control
to the MBR of the "Slave" HD on channel 1.

But most BIOSes give the option to adjust the HD boot order,
and in that situation, the "Master"/"Slave" designation is
ONLY for the IDE controler to differentiate 2 drives on the
same channel (i.e. same cable).

BTW, it matters not a whit which of 2 drives on a cable is
jumpered as "Master". You can jumper the HD at the end
of the cable as "Slave" with the HD at the middle jumpered
as "Master", and the IDE controler will still be happy because
all it's interested in is that the drives are jumpered differently.

The Cable Select mode is only to give PC assembly personnel
less of a headache when setting up a PC and to prevent
owners from jumpering both drives the same way. The
industry had to decide whether to make the end connector
"Master" or "Slave", and they arbitrarily chose "Master".

*TimDaniels*
.

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