IBM p5 550, Technical Overview And Introduction

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Chapter 2. Architecture and technical overview
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The remote HMC and the Web-based System Manager Remote Client allow you the flexibility
to access your managed systems (including HMCs) from multiple locations using multiple
HMCs.
For more detailed information about the use of the HMC, refer to the IBM Systems Hardware
Information Center.
Open Firmware
A System p5 server has one instance of Open Firmware both when in the partitioned
environment and when running as a full system partition. Open Firmware has access to all
devices and data in the server. Open Firmware is started when the server goes through a
power-on reset. Open Firmware, which runs in addition to the Hypervisor in a partitioned
environment, runs in two modes: global and partition. Each mode of Open Firmware shares
the same firmware binary that is stored in the flash memory.
In a partitioned environment, Open Firmware runs on top of the global Open Firmware
instance. The partition Open Firmware is started when a partition is activated. Each partition
has its own instance of Open Firmware and has access to all the devices assigned to that
partition. However, each instance of Open Firmware has no access to devices outside of the
partition in which it runs. Partition firmware resides within the partition memory and is
replaced when AIX 5L or Linux takes control. Partition firmware is needed only for the time
that is necessary to load AIX 5L or Linux into the partition server memory.
The global Open Firmware environment includes the partition manager component. That
component is an application in the global Open Firmware that establishes partitions and their
corresponding resources (such as CPU, memory, and I/O slots), which are defined in partition
profiles. The partition manager manages the operational partitioning transactions. It responds
to commands from the service processor external command interface that originates in the
application running on the HMC.
The ASMI can be accessed during boot time or using the ASMI and selecting the boot to
Open Firmware prompt.
For more information about Open Firmware, refer to Partitioning Implementations for IBM
eServer p5 Servers, SG24-7039, found at:
http://www.redbooks.ibm.com/abstracts/sg247039.html