[c-nsp] 6500/7600 "reserved" power for secondary sups

[Ian Cox]

At 04:39 PM 3/3/2006 -0500, Richard A Steenbergen wrote:
>On Fri, Mar 03, 2006 at 01:19:06PM -0800, Ian Cox wrote:
> >
> > No.
> >
>...
> >
> > This is by design. We need to be able to handle the case of plugging
> > in a redundant supervisor and having it power up. You can place your
> > line card into the redundant supervisor slot.
>
>Lets say for example that someone was buying colo from a particular vendor
>who was too retarded to deliver a 220V AC circuit on time. Lets say that
>someone wanted to turn up box on 110V now, and then move to 220V when
>previously mentioned retarded colo vendor got their act together. Lets
>also say that there is enough actual power to run on one power supply
>during the move (so that you could switch one power supply at a time and
>have no impact during the transition), but there isn't enough to run the
>actual power + account for the phantom supervisor.
>
>What happens if you pull the second power supply? Does it sacrifice a real
>card in order to keep power available for the phantom slot?

Yes. Modules are powered down starting from the highest number slot to lowest.

>  Other than
>putting something else in its place (which means doing a card move after
>the fact to free up slot 6 if you ever DID want to put a second sup
>there), wouldn't it make sense for there to be an option to completely
>disable this slot and its associated power if you knew you weren't going
>to be using it?

The complication is that the Supervisor is special in regards to 
power up. They are set to power up upon insertion because if they are 
the only one in the system they are needed to power up, and they can 
be in either slot. They can only work that they are the only one in 
the system when the software on them boots. How would the supervisor 
ever power up if just one is in the system. There is no logic on the 
board of supervisor to determine what other modules are inserted 
until the CPU is up and running. There would have to be logic added 
to supervisor that would send messages out before the system boots to 
work out if another supervisor is present and active and then tell it 
to act like a regular line card in regards to power management. That 
makes every much more complicated, therefore the rule about 
supervisor slots and power.


Ian

>#no power enable module 6
>% module is not present
>
>--
>Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
>GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)