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Chapter 1
Overview
Cooling System
28
Cooling System
The Superdome has four blowers and five I/O fans per cabinet. These components are all hot-swap devices. All
have LEDs indicating the current status. These LEDs are self-enplanation. Temperature monitoring occurs
for the following:
- Inlet air for temperature increases above normal
- BPS for temperature increases above normal
- The I/O power board over temperature signal is monitored.
The inlet air sensor is on the main cabinet, located near the bottom of cell 1 front. The inlet air sensor and the
BPS sensors are monitored by the PM3 (on the UGUY), and the I/O power board sensors are monitored by the
cabinet level utilities (CLU) (on the UGUY).
The PM controls and monitors the speed of groups of N+1 redundant fans. In a CPU cabinet, fan Group 0
consists of the four main blowers and fan Group 1 consists of the five I/O fans. In an I/O Expansion (IOX)
cabinet, fan Groups 0 thru 3 consist of four I/O fans and fan Group 4 consists of 2 management subsystem
fans. All fans are expected to be populated at all times (with the exception of the OLR of a failed fan).
The main blowers feature a variable speed control. The blowers operate at full speed there is circuitry
available to REDUCE the normal operating speed. All of the I/O fans and managed fans run only at 1 speed.
The PM controls fans through the use of the following resources:
- fanReference D/A (for main fans only)
- tachSelect register
- 930 Port 3.5 (T1) and 930 Timer 1
- FAN_SPEED_HIGH and FAN_SPEED_NORMAL message (for main fans only)
- 16 blower/fan present signals
- 2 manageability fan present signals
- 16 blower/fan fail signals
- 2 management fan fail signals
When the PM queries the entities for their maximum power consumption, the cells also send a value
describing the desired NORMAL main fan speed. Cells of the same architecture send identical values. If the
PM receives differing values, it uses the largest value.
One minute after setting the main blower fanReference to the desired speed or powering on the cabinet, the
PM uses the tach select register to cycle through each fan and measure its speed. When a fan is selected,
Timer 1 is used in counter mode to count the pulses on port T1 over a period of 1 second. If the frequency does
not equal the expected frequency plus some margin of error, the fan is considered to have failed and is
subtracted from the working fan count.