IBM E850C Technical Overview And Introduction Download

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IBM Power System E850C: Technical Overview and Introduction

2.4 Memory subsystem

The Power E850C can have two, three, or four processor modules installed per server. Each
processor module enables eight DDR4 CDIMM slots capable of supporting 16 GB, 32 GB,
64 GB, and 128 GB CDIMMs. A server with four processor modules can support up to 4 TB of
installed memory, a server with three processor modules installed can support up to 3 TB of
installed memory, and a server with two processor modules installed can support up to 2 TB
of installed memory.

The memory on the systems is Capacity on Demand-capable, allowing for the purchase of
additional memory capacity and dynamically activate it when needed. It is required that at
least 50% of the installed memory capacity is active.

The Power E850C server supports an optional feature called

Active Memory Expansion

(#4798). This features allows the effective maximum memory capacity to be much larger than
the true physical memory maximum. Sophisticated compression and decompression of
memory content by using the POWER8 processor along with a dedicated coprocessor
present on each POWER8 processor can provide memory expansion up to 100% or more.
This ratio depends on the workload type and its memory usage. As an example, a server with
256 GB of RAM physically installed can effectively be expanded over 512 GB of RAM. This
approach can enhance virtualization and server consolidation by allowing a partition to do
more work with the same physical amount of memory or allowing a server to run more
partitions and do more work with the same physical amount of memory. The processor
resource used to expand memory is part of the processor entitlement assigned to the
partition enabling Active Memory Expansion.

Active Memory Expansion is compatible with all AIX partitions. Each individual AIX partition
can have Active Memory Expansion enabled or disabled. Control parameters set the amount
of expansion wanted in each partition to find a balance of memory expansion and processor
utilization. A partition needs to be rebooted to turn on Active Memory Expansion.

A planning tool is included within AIX that allows you to sample actual workloads and
estimate the level of expansion and processor usage expected. This tool can be run on any
Power Systems server running PowerVM as a hypervisor. A one-time, 60-day trial of Active
Memory Expansion is available on each server to confirm the estimated results. You can
request the trial activation code on the IBM Power Systems Capacity on Demand website:

http://www.ibm.com/systems/power/hardware/cod

To activate Active Memory Expansion on a Power E850C server, the chargeable feature code
#4798 must be ordered, either as part of the initial system order or as an MES upgrade. A
software key is provided which is applied to the server. There is no need to reboot the system.

2.5 Memory Custom DIMMs

Custom DIMMs (CDIMMs) are innovative memory DIMMs that house industry-standard
DRAM memory chips and a set of components that allow for higher bandwidth, lower latency
communications, and increased availability. CDIMMs include these components:

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Memory Scheduler

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Memory Management (RAS Decisions and Energy Management)

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Memory Buffer