[c-nsp] power requirement for sup720 migration

[Jay Ford]

On Wed, 15 Nov 2006, Gert Doering wrote:
> On Wed, Nov 15, 2006 at 12:02:16PM -0600, Jay Ford wrote:
> > No, that will not work.  The sup720 needs a high-speed fan.  The high-speed
> > fan needs at least a 2500 W power supply.  Therefore, you can't run a 6500
> > containing a sup720 on 1300 W power supplies, even in combined
> > (non-redundant) power mode.
>
> Please don't tell that to our 7600s...
>
> Cisco>sh power
> system power redundancy mode = redundant
> system power total =     1370.04 Watts (32.62 Amps @ 42V)
> system power used =       773.64 Watts (18.42 Amps @ 42V)
> system power available =  596.40 Watts (14.20 Amps @ 42V)
>                         Power-Capacity PS-Fan Output Oper
> PS   Type               Watts   A @42V Status Status State
> ---- ------------------ ------- ------ ------ ------ -----
> 1    PWR-1400-AC        1370.04 32.62  OK     OK     on
> 2    PWR-1400-AC        1370.04 32.62  OK     OK     on
>                         Pwr-Allocated  Oper
> Fan  Type               Watts   A @42V State
> ---- ------------------ ------- ------ -----
> 1    FAN-MOD-3HS         125.16  2.98  OK
>                         Pwr-Requested  Pwr-Allocated  Admin Oper
> Slot Card-Type          Watts   A @42V Watts   A @42V State State
> ---- ------------------ ------- ------ ------- ------ ----- -----
> 1    WS-SUP720-3B        282.24  6.72   282.24  6.72  on    on
> 2    WS-X6408A-GBIC      282.24  6.72   282.24  6.72  on    on
> 3    WS-X6408A-GBIC       84.00  2.00    84.00  2.00  on    on
>
> (This is a 7603, but e.g. for the 7604, the power requirements for the
> highspeed fan module is even lower, 54 Watts)
>
> Originally, this box came with 900W PSUs.  Which is plenty, given that
> the Sup720-3B only needs 300W.

I guess that's a reason to go 7600 instead of 6500. ;^)

> So this whole thread is confusing me.  What are you doing to your modules
> that a 6748 + Sup720 will need 3000W?  (PoE maybe?)

I don't need the 2500 or 3000 W for line cards.  My hands-on experience is
that if I put a high-speed fan try in a 6506 or 6509 with a 1300 W supply the
switch will declare the 1300 W supply as incompatible with the fan try & the
switch shuts down.  The power math never comes into play because the 2500 W
supply seems to be a basic hard requirement of the high-speed fan.  Thus,
I've put at least 2500 W supplies in all our 650[69] chassis which have
sup720 & thus high-speed fans.  This is a damn nuisance, but seemed
necessary.

The 760x is apparently different. For all I know the 6509-E might be
different, too. The Cisco power calculator is the right way to answer these
questions:
   http://tools.cisco.com/cpc/launch.jsp

________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email: jay-ford at uiowa.edu, phone: 319-335-5555, fax: 319-335-2951