Essay: Memory Design and Structure of z9 Mainframes

Sample Essay

In System z9 Mainframes, the size of maximum memory depends directly on the number of Books in the system. Physical memory in each book is organized into two banks of four DRAM memory slots each with one slot from each bank always populated. The size of memory per bank can different and each slot can also have a different amount of memory. An important fact to mention here is that in System z9 Mainframes, IBM can installed more memory than purchased, however, this excess memory would not be accessible. Memory upgrading in System z9 is achieved through purchasing a License Internal Code from IBM, which whole or part of the memory, depending on the Code Purchased.

3.2.1.   Hardware System Area (HSA)

The Hardware System Area (HSA) is a non-addressable storage area in the memory of System z9 Mainframe. It contains the service Licensed Internal Code and configuration dependent control blocks. HSA memory is utilized by a number of internal functions, but mainly by channel subsystem functions.  Each subchannel present in each of the logical partition defined takes up 256 bytes in the HSA. The size of HSA in System z9 Mainframe can be twice that of HSA in previous systems due to the double number I/O devices supported by the Mainframe through multiple subchannel sets.

3.2.2.    Memory Bus Adapter

In IBM System z9 Mainframe, the CEC Cage is connected to the I/O Cage through STI links originating from Memory Bus Adapter (MBA) module of the Books. Each book contains up to eighth MBA modules and each of these MBAs provides connectivity of two STI links (Emery, 2005).

4.         I/O System

The System z9 I/O system has been designing to provide high performance and availability as well as excellent flexibility. It allows for these features through high bandwidth availability, wider connectivity options, cryptographic processing, and support for concurrent upgrades as well as dynamic I/O configuration. It supports a number of I/O feature ports such as ESCON, FICON, OSA-Express and Integrated Cluster Bus. It provides this support through the use of I/O cages which are connected to the CEC Cage holding Books via a number of high-speed Self-Timed Interconnect (STI) links.

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