Conference netcad::hub_mgnt

640.0. "DEChub900 Power Management" by QUIVER::SLAWRENCE () Wed Jan 19 1994 20:31

[I didn't write this, I'm just posting it here - SL]
    
    If you have questions about any of the following, it might be better if
    you posted a new note; we'll put follow-ups here for changes or
    clarifications. - SL
    
    ===================================================================

                        DecHub900MS Power Management
                        ----------------------------


Overview/Background
-------------------
This is a informational document on how power is managed in a DecHub900, from
the perspective of the Management Agent FW.

To be backwards compatible with the DecHub90, MIN modules are automatically
powered up when inserted into a DecHub900, without the intervention of the
power manager. MAX modules on the other hand, are not enabled (powered
on) when inserted into a DecHub900.

Power management is required on the DecHub900 primarily to prevent MAX
modules from being enabled (powered on) when there is not enough power
available to give. Power management also safeguards the total system should
power supplies fail (no battery backup feature).

Equations
---------

  DecHub Power Supplies:

        A power supply has 3 operational LIMITS (RATING) :

                . how much 5v power can be supplied.
                . how much 15v power can be supplied.
                . how much total power can be supplied.

          where, (5v power) + (15v power) DOES NOT EQUAL (total power)
          and, any ONE of these limitations when reached, will cause
          MAX modules to be powered down!

        * A maximum of 4 power supplies can be installed onto the DecHub900.
          Currently, only the DecHub900 140W power supplies are available. Due
          to their low efficiency rate (AC->DC) on the DecHub900 140W power
          supplies, a MAXIMUM of 420w (3 supplies) can be made available for
          comsumption even when 4 supplies are installed onto the DecHub900. As
          a result, the DecHub900 with 4 power supplies will ALWAYS have N+1
          redundancy and a available supply of 420W power.

  12v Usage:

        The 12v power from the DecHub900 backplane is really from a
        15v power source. The 12v power is rectified (voltage regulator
        circuit) from the 15v power source on the DecHub900 backplane.
        To calculate 15v power from 12v power (vice versa):

          wattage (work done) / voltage (potential) = current (rate)

           Xwatts = 12Volts * YAmps  --->   Zwatts = 15Volts * YAmps

                           where, Xwatts < Zwatts

Algorithm
---------

  Priority Scheme :

        - Power allocation is performed starting with slot8 down to slot1.

        - ALL MIN modules within the DecHub900 are given FIRST consideration
          for power since they are automatically powered up.

        - If a MAX module cannot be powered up, ALL MAX modules following
          that one, are prevented from being powered up EVEN if any of those
          MAX modules could have been. This provides predictability and
          consistency of the total system.

                ie: slot1,slot3,slot5 has MAX modules in them.
                    Cannot supply power to slot5, so slot3, slot1
                    are powered on or not turned on even if slot3
                    and/or slot1 uses much less power than slot5.

        - Powering down of MAX modules starts with slot1 up to slot8 when
          the total system power availability drops below 0watts.

  Defaults Given :

        - All MIN modules upon insertion are automatically assumed to be
          consuming 7w of 5v and 0w of 15v. When a MIN module is operational,
          the ACTUAL consumption numbers are determined by the power manager,
          via a lookup table.

        - All MAX modules upon granted power to be enabled, automatically
          receives 7.5w of 15v for their 2 fans. Additional 15v power is
          requested through power arbitration with the power manager and
          the MAX module.

  Functionality :

        - The priority scheme is performed whenever:

                . DecHub900 is powered up or reset.
                . A hub module is inserted or removed.
                . A hub modules' power requirements has been changed
                  (power arbitration).
                . A power supply is inserted or removed.
                . A power supply: good->bad, bad->good, on->off, off->on

        - If a any hub module goes to temp red, or shuts itself off, the
          power manager will exclude that module from future priority scheme
          calculations. If that same hub module drops back to temp yellow,
          then it is included in future priority scheme calculations.

        - If any hub module (MAX or MIN) is removed from the DecHub900 and
          WAS utilizing power, the power manager will attempt to power up
          other MAX modules that were not enabled previously using the
          priority scheme.

        - FOR MAX MODULES: How the power manager determines the modules power
                           requirements.

                . When a MAX module is in the DecHub900, the power manager
                  will determine if it is a MIN or a MAX module. This is
                  performed by reading the power CSRs on the DecHub900
                  backplane (0xFF mean MIN, otherwise MAX). This value also
                  identifies the 5v power requirements. The 5v power
                  requirements is the minimum amount of which the module can
                  be enabled (power up). Enabling of a MAX module in terms
                  of the power managers point of view, is the following check:

                    (total available power) >= (the 5v power + 7.5w of 15v)

                  Once the MAX module is "up", the power manager will request
                  the modules' FULL 15v requirements. This is called power
                  arbitration. Once the FULL 15v requirements have been
                  received, this value becomes the REAL power requirements of
                  that module and the power manager replaces this new value
                  with the old value for the module and then a re-calculation
                  of who should be "up" and who should be "down" using the
                  priority scheme is again performed. So, on the MAX modules'
                  perspective, it is either ALL power granted or NO power
                  granted.


  N+1 Redundancy :

        TERM: N+1 redundancy is accomplished when it is possible to remove
              (logically) 1 power supply from the system such that it does
              not affect the hub modules' current power usages. This is to
              maintain system power integrity should any power supply fails.


        - N+1 is attempted whenever:

                . Hub is powered on or reset.
                . A power supply has been inserted or removed.
                . A power supply: bad->good, off->on
                . 1 or more hub modules has been removed.

        - N+1 loss is checked whenever:

                . A power supply is removed.
                . A power supply: good->bad, on->off.
                . 1 or more hub modules has been inserted.


DecHub Module Power Specifications
----------------------------------

MIN MODULE TYPE                 Power Consumption (Watts)
                                 5v   12v  (15v Conversion)
-----------------               ----  ---  ----------------
ANY_OTHERS_NOT_KNOWN             7.0  0.0  <- default values first given

DEChub900 Module                15.0  0.0      0.00
DECbridge_90                     7.0  9.0     11.25
DECbridge 90FL                   7.0  9.0     11.25
DECrepeater 90T                  7.0  0.0      0.00
10BaseT 96JAM                    7.0  0.0      0.00
DECrepeater 90C                  7.0  0.0      0.00
10Base2 96 JAM                   7.0  0.0      0.00
DECrepeater_90FL                 7.0  9.0     11.25
AUI ports 96 bit                 7.0  9.0     11.25
AUI ports 128bit                 7.0  9.0     11.25
DECrepeater 90FA                 7.0  6.0      7.50
AUI/Fiber 96 bit                 7.0  6.0      7.50
DECagent 90                      7.0  6.0      7.50
DECserver 90TL                   7.0  0.0      0.00
DECwanrouter 90                  7.0  0.0      0.00
DECbrouter 90T2                  7.0  9.0     11.25
DECbrouter 90T2A                 7.0  9.0     11.25
DECbrouter 90T1                  7.0  9.0     11.25
DECserver 90TL                   7.0  0.0      0.00
DECserver 90M                    7.0  0.0      0.00
DECserver 90L                    7.0  0.0      0.00
DECserver_90Lplus                7.0  0.0      0.00
DECserver_90Lplus                7.0  0.0      0.00
DECmau 900TL                     4.4  0.0      0.00
DECrepeater 900TL                6.0  0.0      0.00
DECagent 900RA                   6.0  0.0      0.00
DECmau 900TC                     6.0  0.0      0.00
DECrepeater 900FL                6.0  0.0      0.00
DECrepeater 900SL                6.0  0.0      0.00
(OTHERS????)


MAX MODULE TYPE                           Power Consumption (Watts)
                                 5v   15v (default)   15v total w/arbitration
-----------------               ----  ----            ------------------------
DETMM                           20.0  7.50                    8.250
DEFMM                           40.0  7.50                    8.250
DETTM                           20.0  7.50                   15.000
DETMI                            7.5  7.50                    ?????
DSRVZ                           20.0  7.50                    ?????
DEF6X                           40.0  7.50                    8.250
DEFBA                           50.0  7.50                   30.000
DEBMP                           40.0  7.50                   30.000
(OTHERS????)