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Re: Swapping Drives - Sanity Check




Le 23/02/2019 à 17:21, rhkramer@xxxxxxxxx a écrit :
On Saturday, February 23, 2019 10:52:20 AM Pascal Hambourg wrote:
Le 23/02/2019 à 15:41, rhkramer@xxxxxxxxx a écrit :
On Saturday, February 23, 2019 07:53:23 AM Pascal Hambourg wrote:
Le 23/02/2019 à 08:53, David Christensen a écrit :
Understand that if you disconnect the power cable to a motherboard,
drive, peripheral, etc., but not all the other cables (e.g. SATA
cable), you can fry electronics.

Right. This is why power pins are longer than data pins in hotplug
connectors, so that they are connected first and disconnected last.

Hmm, that surprises me -- I guess I would have expected that you want the
data pins connected first (while no power is applied), and disconnected
last (again, while no power is applied).

Why would you want this ? From an electrical or logical point of view,
it makes no sense.

Well, two reasons:

    * in most cases (other than hot plug) you want to make connections first,
before you turn on the power  (I mean, for example, you don't assemble your
computer with the power on)

Most computer parts connections (CPU, RAM, PCI cards...) are not hotplug. For those which are (SATA in AHCI mode), you can connect them while the power is on, power cable first.

Besides, the point is not just about connecting the data pins but applying voltages to them while the device is not powered. If the whole computer is powered off, there is no voltage on data pins.

    * and somewhat similarly (but in a very different context) in a 3 pin power
plug for an ordinary household outlet (in the US), the ground pin is longer
than the power pins so that the ground is connected before power is applied.

This is not similar at all. The ground pin is not a data pin and does not carry any voltage.