HP Cluster Platform Interconnects v2010 Quadrics QsNetII Interconnect - Page 45

6 QM580 Clock Distribution Box This chapter describes the installation, operation, and maintenance of the QM580 clock distribution box. The QM580 clock distribution box provides a global, external clock source for a federated network of interconnects. 6.1 Replacing a QM580 Clock Distribution Box Before replacing a QM580 clock distribution box, ensure that the federated network is using an alternative clock source. For example, before replacing the QM580 clock distribution box that connects the Ctrl A ports, you must set the clock source on each switch to Ctrl B, and vice versa. If a valid alternative clock source is available, it is possible to replace the QM580 clock distribution box without powering down the interconnects. If an alternative clock source is not available, the federated network will stop functioning reliably when the QM580 clock distribution box is powered off. In this case, power down all the nodes and interconnects first to avoid node crashes. To prepare to replace a QM580 clock distribution box, perform the following steps: 1. If you have an alternative clock source, set the clock source for each interconnect to that alternate clock source. If you do not have an alternative clock source, halt and then power down all the nodes and switches. Caution Unless there is an alternate clock source available, a federated configuration will cease to function reliably when the clock distribution box is turned off. If the clock distribution box must be replaced, and there is no alternate clock source available, you must first power down all of the nodes and system interconnects to avoid node crashes. 2. Press the power supply switch (beside the IEC320 power socket) to power down the QM580 clock distribution box. 3. Disconnect the power cable from the IEC320 power socket on the front panel of the QM580 clock distribution box. Use the following procedure to replace a QM580 clock distribution box: 1. If you are replacing a QM580, begin the procedure at Step 2, otherwise go to Step 6 to install a QM580 for the first time. 2. Ensure that all data and power cables are labelled for origin and destination, or record the origin and destination of each cable and mark the cable appropriately. 3. Remove the cables from the rear of the QM580. 4. Working at the front of the rack, remove the four machine screws that secure the QM580 to the rack columns. If you are replacing a QM580, leave the four cage nuts in place. 5. Slide the QM580 out of the rack. QM580 Clock Distribution Box 6-1