[Beowulf] strange PXE reboot behavior

Glen Gardner Glen.Gardner at verizon.net
Thu Sep 16 05:19:08 PDT 2004

You could have a power supply dropping out when the nic comes to life 
and wants more power.
(just an outside guess). Some gigabit nics want a lot of power, and 
motherboard power use at startup can peak to
close to maximunm for the node. If the power supplies are close to their 
nominal limits, you might have some drop
out when the demand increases substantially by means of the nic turning 
on and chatting with the network, causing a
spurious reset/reboot when the peak power use suddenly increases by 
anywhere from 20 watts to as much as 90 watts..


Geoff Galitz wrote:

> Hello folks,
> We have a strange problem. We have 20 nodes with SE7501CW2
> motherboards, and about 5 of them seem to fail their POST and reboot
> only when the gigabit NIC is plugged into a gigabit switch. If we
> unplug it, the node functions normally. If we plug it in after the system
> comes up, it crashes immediately.
> My only thought at this point is auto-negotiation, but I cannot seem to
> turn off auto-negotiation on these motherboard/NIC combos. Ethtool fails
> to change the parameters on the cards.
> Any other ideas?
> -geoff
> http://www.galitz.org
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Glen E. Gardner, Jr.


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