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IBM Power 595 Technical Overview and Introduction
2.1.9 DC converter assembly (DCA)
For the CEC, dc power is generated by redundant, concurrently maintainable dc to dc
converter assemblies (DCAs). The DCAs convert main isolated 350VDC to voltage levels
appropriate for the processors, memory and CEC contained I/O hub cards. Industry standard
dc-dc voltage regulator module (VRM) technology is used.
The DCA does not support multiple core voltage domains per processor. The processor book
planar is wired to support a core voltage/nest domain and a cache array voltage domain for
each of the four MCMs. A common I/O voltage domain is shared among all CEC logic.
Figure 2-12 shows the DCA assembly on the processor book.
Figure 2-12 DC converter assembly (DCA)
When both DCAs are operational, adequate power is available for all operating conditions.
For some technical workloads, the processors can draw more current than a single DCA can
supply. In the event of a DCA failure, the remaining operational DCA can supply the needed
current for only a brief period before overheating. To prevent overheating when load is
excessive, the remaining DCA (through processor services) can reduce the processor load by
throttling
processors or reducing processor clock frequency. Consider the following notes:
Reducing processor clock frequency must be done by the system controller and can take
a long time to accomplish. Throttling can be accomplished much more quickly.
The DCA uses an I2C connection to each processor to accomplish throttling within 10 ms.
Throttling causes the processors to slow down instruction dispatch to reduce power draw.
Throttling can affect performance significantly (by approximately 90% or more).
To regain performance after throttling, the system controller slows down the system clocks
and reduces core voltage, and then unthrottles the processor or processors. This is
effective because slowing the processor clocks and reducing voltage is in turn much more
effective at reducing load than throttling. After a failing DCA is replaced, the system clocks
are returned to normal if needed.
Note:
A special tool is required to install and remove the DCA (worm-screw mechanism).
DC to DC Converter Assemblies
(DCA) 2x
DC to DC Converter Assemblies
(DCA) 2x
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