Penguin Computing Relion 1900e, Technical Manual

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Relion 1900e/2900e Manual
73 Revision 1.3
When a fan is not present, the associated fan speed sensor is put into the reading/unavailable state, and any
associated fan domains are put into the boost state. The fans may already be boosted due to a previous fan
failure or fan removal.
When a removed fan is inserted, the associated fan speed sensor is rearmed. If there are no other critical
conditions causing a fan boost condition, the fan speed returns to the nominal state. Power cycling or
resetting the system re-arms the fan speed sensors and clears fan failure conditions. If the failure condition
is still present, the boost state returns once the sensor has re-initialized and the threshold violation is
detected again.
7.3.14.2 Fan Redundancy Detection
The BMC supports redundant fan monitoring and implements a fan redundancy sensor. A fan redundancy
sensor generates events when its associated set of fans transitions between redundant and non-redundant
states, as determined by the number and health of the fans. The definition of fan redundancy is
configuration dependent. The BMC allows redundancy to be configured on a per fan redundancy sensor
basis through OEM SDR records.
A fan failure or removal of hot-swap fans up to the number of redundant fans specified in the SDR in a fan
configuration is a non-critical failure and is reflected in the front panel status. A fan failure or removal that
exceeds the number of redundant fans is a non-fatal, insufficient-resources condition and is reflected in the
front panel status as a non-fatal error.
Redundancy is checked only when the system is in the DC-on state. Fan redundancy changes that occur
when the system is DC-off or when AC is removed will not be logged until the system is turned on.
7.3.14.3 Fan Domains
System fan speeds are controlled through pulse width modulation (PWM) signals, which are driven
separately for each domain by integrated PWM hardware. Fan speed is changed by adjusting the duty cycle,
which is the percentage of time the signal is driven high in each pulse.
The BMC controls the average duty cycle of each PWM signal through direct manipulation of the integrated
PWM control registers.
The same device may drive multiple PWM signals.
7.3.14.4 Nominal Fan Speed
A fan domain’s nominal fan speed can be configured as static (fixed value) or controlled by the state of one
or more associated temperature sensors.
OEM SDR records are used to configure which temperature sensors are associated with which fan control
domains and the algorithmic relationship between the temperature and fan speed. Multiple OEM SDRs can
reference or control the same fan control domain; and multiple OEM SDRs can reference the same
temperature sensors.
The PWM duty-cycle value for a domain is computed as a percentage using one or more instances of a
stepwise linear algorithm and a clamp algorithm. The transition from one computed nominal fan speed
(PWM value) to another is ramped over time to minimize audible transitions. The ramp rate is configurable by
means of the OEM SDR.