isolating new clone drive for 1st bootup

"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having un-powered
electronics connected to your bus is generally a sure-fire way to drag
the bus down to nothing. This is why hot-swap devices, whether they
are USB or whatever, have connectors that ensure that the power is
applied before the signals are connected.

"chrisv" wrote:
"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having
un-powered electronics connected to your bus is generally
a sure-fire way to drag the bus down to nothing. This is
why hot-swap devices, whether they are USB or whatever,
have connectors that ensure that the power is applied before
the signals are connected.


I was *not* asking about a hot-swap wherein the
logical state of the drive would be undefined when
powered was applied by virtue of the signal cables
being pre-connected. I *was* asking about doing the
switching ON/OFF of power cables while the PC was
shut down. This would be logically equivalent to physically
connecting and disconnecting the power cables to various
HDs by opening the case, etc. I know this works in
some configurations - single HDs on separate channels -
because I've done it. That is, just disconnecting the
power cable of one HD allows the other HD (on the
other IDE channel) to boot up in isolation.

My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered? If the Slave were unpowered and the Master
powered? If Master/Slave positions were reversed? Etc.,
etc. Assuming that the signals "see" a high input impedance at
the HD's circuit card, I'm guessing it wouldn't make a difference
to the channel controller whether the circuitry of the card were
powered on unpowered, i.e. at boot-up, the BIOS would not
see the unpowered device, and the IDE controller wouldn't
try to talk to it, and the dead circuit card's high input impedance
would not drain signals passing by it.

*TimDaniels*

"chrisv" wrote in message news
"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having
un-powered electronics connected to your bus is generally
a sure-fire way to drag the bus down to nothing.

It does work most of the time with removable drive bays.

This is why hot-swap devices, whether they are USB
or whatever, have connectors that ensure that the
power is applied before the signals are connected.

Nope, thats for a completely different reason. And
what they do is ensure that GROUND is connected
first on insertion and disconnected last on removal.

"Timothy Daniels" wrote in message ...

"chrisv" wrote:
"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having
un-powered electronics connected to your bus is generally
a sure-fire way to drag the bus down to nothing. This is
why hot-swap devices, whether they are USB or whatever,
have connectors that ensure that the power is applied before
the signals are connected.


I was *not* asking about a hot-swap wherein the
logical state of the drive would be undefined when
powered was applied by virtue of the signal cables
being pre-connected. I *was* asking about doing the
switching ON/OFF of power cables while the PC was
shut down. This would be logically equivalent to physically
connecting and disconnecting the power cables to various
HDs by opening the case, etc. I know this works in
some configurations - single HDs on separate channels -
because I've done it. That is, just disconnecting the
power cable of one HD allows the other HD (on the
other IDE channel) to boot up in isolation.

My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered?

The short story is that there doesnt need to be
a Master at all. You see that quite a bit with CD
drives as the only drive on a ribbon cable and
most hard drives work fine in that config now too.

The problem is potentially with an unpowered drive physically
connected to the ribbon cable, not the master/slave question.

If the Slave were unpowered and the Master powered?
If Master/Slave positions were reversed? Etc., etc.

Its all irrelevant. What matters is if there is a drive
which isnt powered plugged into the ribbon cable.

Assuming that the signals "see" a high input impedance at
the HD's circuit card, I'm guessing it wouldn't make a difference
to the channel controller whether the circuitry of the card were
powered on unpowered, i.e. at boot-up, the BIOS would not
see the unpowered device, and the IDE controller wouldn't
try to talk to it, and the dead circuit card's high input
impedance would not drain signals passing by it.

That last is the problem, the unpowered ics on the ribbon cable.

"Rod Speed" wrote:

"Timothy Daniels" wrote:
My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered?

The short story is that there doesnt need to be
a Master at all. You see that quite a bit with CD
drives as the only drive on a ribbon cable and
most hard drives work fine in that config now too.

The problem is potentially with an unpowered drive physically
connected to the ribbon cable, not the master/slave question.


Right. I meant a dead device at the *usual position* of a
Master (at the end of the 2-device cable) and the *usual position*
of a Slave (at the mid connector of the cable). My assumption
has been that the roles of Master and Slave on the same channel
were only for device differentiation for the IDE channel controller.
Please correct me if that is wrong.


If the Slave were unpowered and the Master powered?
If Master/Slave positions were reversed? Etc., etc.

Its all irrelevant. What matters is if there is a drive
which isnt powered plugged into the ribbon cable.


Right. Again, I meant the effect of dead (unpowered)
devices at the *usual positions* of Master and Slave. IOW,
does a dead device at either position on the ribbon cable
upset the signals for the other device?

BTW, does is matter a whit if there are 2 devices
(e.g. HDs) on a cable and the device jumpered "Master"
is at the mid connector and the device jumpered "Slave"
were at the end connector? I have been assuming that
there is no difference other than which device will default
to being the boot device. Is that correct?


Assuming that the signals "see" a high input impedance at
the HD's circuit card, I'm guessing it wouldn't make a difference
to the channel controller whether the circuitry of the card were
powered on unpowered, i.e. at boot-up, the BIOS would not
see the unpowered device, and the IDE controller wouldn't
try to talk to it, and the dead circuit card's high input
impedance would not drain signals passing by it.

That last is the problem, the unpowered ics on the ribbon cable.


Yup. That's the question, too. :-)


*TimDaniels*

"Timothy Daniels" wrote:

"chrisv" wrote:
"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having
un-powered electronics connected to your bus is generally
a sure-fire way to drag the bus down to nothing. This is
why hot-swap devices, whether they are USB or whatever,
have connectors that ensure that the power is applied before
the signals are connected.


I was *not* asking about a hot-swap wherein the
logical state of the drive would be undefined when
powered was applied by virtue of the signal cables
being pre-connected. I *was* asking about doing the
switching ON/OFF of power cables while the PC was
shut down.

I didn't think you were trying to hot-swap. I just threw that in as
an example of the importance of never having signals connected to
un-powered devices.

This would be logically equivalent to physically
connecting and disconnecting the power cables to various
HDs by opening the case, etc. I know this works in
some configurations - single HDs on separate channels -
because I've done it. That is, just disconnecting the
power cable of one HD allows the other HD (on the
other IDE channel) to boot up in isolation.

It's not surprising that you can get away with it when there's nothing
else on that bus that needs to work...

My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered?

THAT is what I don't think will work. Rod says it will, and maybe it
will, for some controller/HD combinations. But it's quite hokey to do
that, even if you get away with it.

If the Slave were unpowered and the Master
powered? If Master/Slave positions were reversed? Etc.,
etc. Assuming that the signals "see" a high input impedance at
the HD's circuit card,

That's a big assumption.

I'm guessing it wouldn't make a difference
to the channel controller whether the circuitry of the card were
powered on unpowered, i.e. at boot-up, the BIOS would not
see the unpowered device, and the IDE controller wouldn't
try to talk to it, and the dead circuit card's high input impedance
would not drain signals passing by it.

Timothy Daniels wrote in
message ...
Rod Speed wrote
Timothy Daniels wrote

My question really hinges on the effect of unpowered
devices connected in various combinations and
configurations to a 2-device IDE cable. What would
happen if the Master HD at the end of a cable were
unpowered while the Slave were powered?

The short story is that there doesnt need to be
a Master at all. You see that quite a bit with CD
drives as the only drive on a ribbon cable and
most hard drives work fine in that config now too.

The problem is potentially with an unpowered drive physically
connected to the ribbon cable, not the master/slave question.

Right. I meant a dead device at the *usual position* of
a Master (at the end of the 2-device cable) and the *usual
position* of a Slave (at the mid connector of the cable).

Thats only true of a cable select cable. It doesnt matter
which drive is on which connector with a master/slave config.

My assumption has been that the roles of Master
and Slave on the same channel were only for device
differentiation for the IDE channel controller.

Cant see what the relevance of that is to what is being discussed.

Please correct me if that is wrong.

If the Slave were unpowered and the Master powered?
If Master/Slave positions were reversed? Etc., etc.

Its all irrelevant. What matters is if there is a drive
which isnt powered plugged into the ribbon cable.

Right. Again, I meant the effect of dead (unpowered)
devices at the *usual positions* of Master and Slave.
IOW, does a dead device at either position on the
ribbon cable upset the signals for the other device?

Nope, makes no difference. The only difference
the position makes is when there is just one drive
on the ribbon cable and the end connector has
nothing connected to it. In that situation the unused
bit of the ribbon cable is a stub and you can get a
reflection off the unconnected end with digital signals.

But an unpowered drive on that end
connector should stop most of that.

BTW, does is matter a whit if there are 2 devices
(e.g. HDs) on a cable and the device jumpered
"Master" is at the mid connector and the device
jumpered "Slave" were at the end connector?

Nope, thats fine. The only undesirable config is with
just one drive on the ribbon cable, and that drive on
the middle connector. In that case you have a length
of ribbon cable going nowhere and that can produce
reflections on the cable with digital signals.

I have been assuming that there is no
difference other than which device will default
to being the boot device. Is that correct?

It wont even affect which drive is the boot device.
That is determined by which drive is specified as
the boot drive in the bios and has nothing to do
with which is master or slave or which physical
connector its connected to with a master/slave config.

It does matter with a cable select config where the
master and slave is determined by which connector the
drive is connected to and not the jumpering on the drive.

Assuming that the signals "see" a high input impedance at
the HD's circuit card, I'm guessing it wouldn't make a difference
to the channel controller whether the circuitry of the card were
powered on unpowered, i.e. at boot-up, the BIOS would not
see the unpowered device, and the IDE controller wouldn't
try to talk to it, and the dead circuit card's high input
impedance would not drain signals passing by it.

That last is the problem, the unpowered ics on the ribbon cable.

Yup. That's the question, too. :-)

"Rod Speed" wrote:

"chrisv" wrote in message news
"Timothy Daniels" wrote:

It would be a lot easier if one could just shut down
and then disconnect the other drives by use of a
physical switch to break the connection with their
power cables. That would avoid all the hassle of
opening the case and unplugging the other drives.

So, does anyone have any information that would
indicate if switching the power cables would work?

I'd be very surprised if you get away with that. Having
un-powered electronics connected to your bus is generally
a sure-fire way to drag the bus down to nothing.

It does work most of the time with removable drive bays.

I'm not familiar with these... Are you saying they leave multiple
drives connected to a bus, with some of those drives not powered?

This is why hot-swap devices, whether they are USB
or whatever, have connectors that ensure that the
power is applied before the signals are connected.

Nope, thats for a completely different reason.

Well, it allows the device's reset circuitry to bring things to a
known state, as well... I don't think your "nope" is warranted,
however.

And what they do is ensure that GROUND is connected
first on insertion and disconnected last on removal.

Maybe with some hot-swapable devices, but not all. USB clearly
connects power and ground at the same time, as does Compact PCI
(cPCI).

http://www.intersil.com/data/tb/tb386.pdf

http://www.quicklogic.com/images/cpci.pdf

chrisv wrote:

"Timothy Daniels" wrote:

My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered?

THAT is what I don't think will work. Rod says it will, and maybe it
will, for some controller/HD combinations. But it's quite hokey to do
that, even if you get away with it.

If the Slave were unpowered and the Master
powered? If Master/Slave positions were reversed? Etc.,
etc.

I should have noted that switched master and slave around is
irrelevant to this situation.

"chrisv" wrote:
"Timothy Daniels" wrote:
My question really hinges on the effect of unpowered
devices connected in various combinations and configurations
to a 2-device IDE cable. What would happen if the Master
HD at the end of a cable were unpowered while the Slave
were powered?

THAT is what I don't think will work. Rod says it will,
and maybe it will, for some controller/HD combinations.
But it's quite hokey to do that, even if you get away with it.


Hey! The whole scheme is hokey, including the removable
drive tray/rack. I just want to know if it *works*. If it works,
it would save a whole bunch of labor, and it would encourage
me to do backups more often.

*TimDaniels*