Conference netcad::hub_mgnt

    Can you determine the hardware and firmware revision of this
    DECbridge 900MX? This behavior is something we have seen with
    an older rev firmware than 1.2.1 here in engineering at LKG.
    
    Bob

    This is a problem that was seen on v1.1.2, the "early ship" version
    of DB900MX firmware.  Please upgrade to v1.2.1, the current released
    version.  The firmware image can be downloaded from the Internet:
    ftp.digital.com, directory /pub/DEC/hub900/firmware, filename
    db900mx_v121.bin.

    Some more detail: at 30 degrees, the fans on the DECbridge module
    kick into high speed.  In v1.1.2, this was signalled to the
    Hub Manager as a "Yellow temp" condition and interpreted as
    a non-fatal error.  Since this is a normal temperature, and
    adequate cooling continues to be provided, we decided to get rid of
    the unnecessary warning.  If temperature gets critical (somewhere around
    55 as far as I can remember), this would be reported by the module as a
    "Red Temp" condition.

    Anil

    Thanks!!
    
     I confermed DB900 Firmware version. It is v1.1.2.
     I will update to firmware v1.2.1 soon.

     And more question .
     
     What is the sensing point of " over temp yellow " at DECbridge
     firmware v1.2.1 ?  About 40 degree ?

    I think it's around 40�-45�C for DB900MX units of the most recent
    hardware revision currently shipping from manufacturing with the
    firmware rev v1.2.1
    As Anil alluded to, the trip point for earlier hardware shipped
    was a lower temperature of around 35�C, thus the firmware was
    reporting the "over temp yellow" at an unnecessarily low temperature.
    
    Bob

    As Anil stated, the firmware no longer reports the temp yellow warning
    since it is a normal condition.  Since there is no warning, the only
    effect of the temp yellow condition will be to kick the fans to high
    speed.
    
    I don't know whether or not the temp yellow condition warning has been
    supressed in other products.
    
    For all the repeaters, temp yellow is set such that the condition
    occurs when the outside ambient reaches 30C.  At this point, the fans
    go to high speed.  There is a second trip point, temp red, which
    indicates a catastrophic condition as the ambient temperature inside
    the box has reached 70C.
    
    Products currently on the drawing board have made a change in this
    area. There are three trip points.  The lowest will be at 30C outside
    ambient and will only control the fans.  Temp red will remain the same,
    and temp yellow will be set a few degrees below temp red.  For products
    with this new scheme, it will make sense to once again report temp
    yellow condition, because it will then truly be a warning of something
    going wrong.

re: .-1

>    For all the repeaters, temp yellow is set such that the condition
>    occurs when the outside ambient reaches 30C.  At this point, the fans
>    go to high speed.  There is a second trip point, temp red, which
>    indicates a catastrophic condition as the ambient temperature inside
>    the box has reached 70C.

Earlier reply has different figures for bridges. Which is correct?

Thanks,
_Tak

    I'm describing the operation of the MAX repeaters... DETMM, DETTM, and
    DEFMM.  I can't speak for where the bridge folks put their setpoints.

    Here is a more fine-tuned answer to where our set points for the 
    DB900MX are currently placed. My previous answer of 35�-45� was
    in error.
    Currently our hardware is designed for the original 2-set point
    scheme. That is, when the fans, go to high speed, the yellow
    zone trip point (on temperature rising) is reached at 30�C.
    Ergo we have one voltage comparator functioning for both the 
    yellow zone trip point indication, and to trip the circuit that
    turns the fan into high speed. On temperature falling, fans
    are kicked back to low speed at 25�C. So the yellow zone has
    a hysteresis between 25�C-30�C to prevent it from oscillating
    between fan speeds. 
    A second voltage comparator circuit monitors and trips the red zone
    set point. Red zone trips on at 63�C (on rising temp), and trips off 
    at 58�C. 
    All the above temperatures are room ambient (outside the DB900MX
    box enclosure).
    The DB900MX has about an 8�C-10�C temperature rise, thus the reason
    for picking the red zone trip point.
    The yellow zone trip point temperature is fine for turning fans to 
    high speed, but the yellow zone warning messages were seen as being
    distracting, and are non-fatal in nature. So they are surpressed,
    but the fans still turn to high speed at rising temperature of 30�C.
    
    Bob

Thank you both for the clarifications.

Ref: 
>    Products currently on the drawing board have made a change in this
>    area. There are three trip points.  The lowest will be at 30C outside
>    ambient and will only control the fans.  Temp red will remain the same,
>    and temp yellow will be set a few degrees below temp red.  For products
>    with this new scheme, it will make sense to once again report temp
>    yellow condition, because it will then truly be a warning of something
>    going wrong.

What does DEC Standards have to say in this area, I mean a recommended
operating temparature range?   From a customer's perspect, temp yellow of 
'a few degrees' below temp red (~63C) would mean too high this time..  
Hubs are likely to be placed in an "office" enviorinment.  Is around 60C 
realistic point to show a yellow condition?   My interpretation to yellow
condition would be a point that should reserve a customer action to fix 
their evironmental problem. 

_Tak

    >>  What does DEC Standards have to say in this area...
    
    All products must pass a thermal qualification.  Each product has a
    rated operating temperature range.  For the majority of hub components,
    the maximum temperature is 50C ambient.
    
    The thermal qualification consists of running the product at maximum
    ambient temperature and measuring the case temperature (with
    thermocouples) of any component on the modules which tend to run hot
    (based on an infrared pre-screen of the module).  From the case
    temperatures, the corresponding junction temperatures are estimated and
    compared to established maximum allowable limits.  The limit varies
    depending on the type of component (bipolar, CMOS, etc.).  In my
    experience, the DEC standard for maximum allowable junction
    temperature is stricter than the manufacturer's limits.
    
    >>  From a customer's perspect, temp yellow of 'a few degrees' below 
    >>  temp red (~63C) would mean too high this time..
    
    Right.  The intention is for the temp yellow indication to mean that
    the ambient temperature is above the rated maximum for the product
    (50C) or something is broken in the product and it is running too hot.
    Thus, reporting the temp yellow will be warrented, as it means temp red
    (and shutdown) is not too far away.
    
    >>  Is around 60C realistic point to show a yellow condition?   My 
    >>  interpretation to yellow condition would be a point that should 
    >>  reserve a customer action to fix their evironmental problem.
     
    The intention will be that a temp yellow warning not be posted falsely,
    but be an indicator of a real problem.  So if a module is measuring a
    temperature which corresponds to 60C ambient, either the product is in
    an environment beyond what it is rated for (that problem would need to
    be fixed) or the product is experiencing an abnormally high temperature
    difference between the outside ambient and the inside (which also
    indicates a problem which needs to be fixed).  Either way, temp yellow
    will indicate something needs to be fixed.
    
    >>  Hubs are likely to be placed in an "office" enviorinment.
    
    Right again... and this is why we need a control point for the fans of
    about 30C.  In the office, we need the fans to run slow in order to
    meet acoustic requirements.  Once we're in a closet, as indicated by
    30C or higher ambient, we want the fans to run fast because we don't
    need to worry about acoustics and we want the product to run cool for
    increased reliability.

Thanks.  I still have one thing unclear which lead me to wonder why ~60C is
(will be?) chosen as the temp yellow.

That is - how do you define 'office' environment?  

Although I can't speak for all possible office environment temparature ranges
in the world, here in Japan, I would be surprised to see ~40C.  No one wants 
to get to work. :-)   On weekend in summer, where no air conditioning 
activated, there *might* possibly be ~50C depending on rooms with windows 
facing the sun (just guess).  To me, ~60C is unrealistic office environmental 
condition; I can't see any difference between ~60C and ~63C. - both means that 
something is definitely going wrong. 

>    >>  What does DEC Standards have to say in this area...
>    
>    All products must pass a thermal qualification.  Each product has a
>    rated operating temperature range.  For the majority of hub components,
>    the maximum temperature is 50C ambient.

Given that the maximum temperature of 50C, a trip point at 50C for the temp
yellow sounds rather realistic to me.  I could talk customers into preparaing 
air conditioning for weekend, because it hits our operating temperature upper
limit; it will not be a false warning, I believe.

_Tak
Ps. when the shutdown actually start? - right after temp. red? 

    >>  ...how do you define 'office' environment?
    
    I was discussing "office environment" only in the context of fan speed 
    switching.  In that context, detecting outside ambient of 30C or higher 
    means we may run the fans fast.
    
    >>  Given that the maximum temperature of 50C, a trip point at 50C for 
    >>  the temp yellow sounds rather realistic to me.
    
    I have to disagree here.  If the product is rated for 50C and we set
    temp yellow at 50C, we'll have the same problem stated in the base
    note, i.e., false warnings.  There has to be some margin built in so
    that temp yellow is a definite warning of something going wrong.
    
    >>  When the shutdown actually start? - right after temp. red?
    
    Yes.  The intention is for modules to shut down when they detect a temp
    red condition.  The first line of defense is software... the code logs
    the condition to the hub manager and then shuts down.  There is also
    hardware built in which will shut down the module if the watchdog timer
    expires in the presence of a temp red condition.
    
    A reminder: all this discussion applies only to MAX (large, 900)
    modules.  The MIN (small, 90) modules, even the new ones such as DEFMI 
    and DETMI, have neither temperature sensing nor power control which 
    would allow them to shut down. 

    

Re: .-1   Thanks.

>    >>  Given that the maximum temperature of 50C, a trip point at 50C for 
>    >>  the temp yellow sounds rather realistic to me.
>    
>    I have to disagree here.  If the product is rated for 50C and we set
>    temp yellow at 50C, we'll have the same problem stated in the base
>    note, i.e., false warnings.  There has to be some margin built in so
>    that temp yellow is a definite warning of something going wrong.

Ok.. That's a matter of definition of Warning.   I'm then confused why
~30C was defined for a warning point in the first place.  I guess I want to  
see some 'notification' at ~50C, which may help customers to prepare
some action in advance, before something is definitely going wrong.    
(I can understand a need of some margin.)  

_Tak

    The initial design had temp yellow condition defined as the spot where
    we wanted the fans to go to high speed.  This we wanted to be at 30C.
    
    The whole problem is that this shouldn't be a system warning, so we
    stoped reporting it as such.  Now there's no warning for impending temp
    red.  So we're fixing the whole thing by adding another temperature
    comparator.  Then we'll have discrete temperature levels for fan
    control, temp red, and temp yellow, which will (finally) mean warning
    of something wrong.