How to esimate power consumption?

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Mar 20th, 2008
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I recently had the shocker of installing a new card in my 6509 to find that it went into PwrDeny state. Taking a closer look via "show power" I saw the twin 2500W power supplies listed as actually pumping out less than half that power.

Question 1: Shouldn't a 2500W power supply provide 2500W of power?

Question 2: Where can I go to estimate the power needs of individual cards and the power provided by different supplies to avoid this in the future?

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Samuel8rown Thu, 03/20/2008 - 23:55
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Hm. That's a step forward. I see here where it shows that a Sup720 (like we have) sucks down 315 watts. Though it doesn't say is that the system actually reserves double that power for it.

So far my google-fu has only turned up spec-sheets on power supplies 6000W and above. I see in those specs where all the power supplies output considerably lower wattage than they input, though at higher amperage. (More than meets the eye, it would seem.)

Samuel8rown Fri, 03/21/2008 - 00:00
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Any reason I shouldn't shut off the power it's reserving for the non-existant backup Sup card with ye olde "no power enable module #" command?

Samuel8rown Fri, 03/21/2008 - 10:37
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Apparently that doesn't work. Shutting power off to a non-existant card generates the message:

% module is not present

...and the 6509 continues to allocate power to it.

Mark Yeates Sat, 03/22/2008 - 13:41
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Are you using 120 or 220 volts to the power supplies? You must use 220 to achieve the full output with each power supply. If you are using 120 then you are only getting half of the total output.

Here is a link to the Cisco Power Calculator.


Samuel8rown Sat, 03/22/2008 - 15:31
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Thanks. I'd found that out peicemeal along the way. Had I read that early on, it would have saved me a lot of trouble. That, and the whole deal with the system reserving power for a redundant supervisor card that we will never install. Humbug.


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