Specifications

6
Troubleshooting
107
EachIPMCthatisnottheactiveShMCmonitorsits“ownside”ofthebus.Inotherwords,
eachIPMCismonitoringitsownI
2
CinterfacesthatareconnectedtoIPMB‐AorB.Periodically
itchecksforerrorsontheI
2
CinterfacesusingregistersintheIPMC.Ifanerrorisdetected,the
IPMCisolatesitselffromtheIPMB,resetsitself,andtriestorejointhebus.IftheIPMCisnot
successful,itgeneratestheIPMB‐0sensoreventviatheotherbusandkeepsitselfisolated
fromtheerror‐pronebus.TheIPMCperiodically(every250msecs)triestoresettheI
2
C
interfaceandrejointheerror‐pronebusuntiltheerrorcorrects.
TheactiveShMChastheresponsibilityofmonitoringnotonlyitsownsideoftheIPMBbut
alsotheexternalIPMB.Itcanthusdetectifsomeothererror‐proneIPMCinthechassisis
holdingoneoftheIPMBsdown,andisolateitselffromthatbus.Alltransactionsarethen
doneontheotherbus.PeriodicallytheShMCwilljointheerror‐pronebustotestiftheerror
isstillthere.
IPMB and IPMC failure problems
AllIPMCsarbitratetogetaccesstothebus,butmessagescanbemissedifthereisalotof
trafficonthebus(e.g.runningastresstest),andallmessagingbuffe rsontheIPMCarefull.
EachIPMCretriesrequeststhreetimesandtheShMSretrieseachrequest5times.Also,hot‐
swapeventsareguaranteedtobereceivedbecausetheygetretrieduntiltheShMS
acknowledgesthem.Thisensuresthatnohot‐swapeventislost.TheIPMC'seachhavea50
messagebuffer,andtheShMChasroomforanadditional10messages.Thechanceof
overrunningthemessagebuffersislow,butitispossibleifeverybladeinthechassis
simultaneouslygenerateseventsfrommultiplesensors.
MessagecorruptioncanhappenontheIPMBunderlimitedcircumstances,suchaswhenthe
IPMCisreceivingandformattingthemessageduetoalocalIPMCerror.Ifthemessageis
corrupted,theIPMCchecksboththeheaderandthemessagechecksum.Ifeithertheheader
orchecksumisincorrect,themessageisdropped.ThesendingIPMCthenretriesthe
message.Thereislittlechanceofthesamemessagegettingcorruptedonthebusthreetimes
insuccession.
If IPMB-0 Isolation events are seen frequently in Event Log
Thefollowingeventsmighthaveasimilarcause:
•AFRUsendsfrequentIPMB‐0Isolationevents
•TheactiveSCMreportsfrequentIPMB‐0Isolationevents
•TheShMSisunabletocommunicatewithshelfIPMCsbecauseoffrequentIPMB‐0
Isolationissuesintheshelf