6947ch01.fm Draft Document for Review April 7, 2004 6:15 pm
6 IBM eServer zSeries 990 Technical Guide
򐂰A System Assist Processor (SAP)
򐂰An Internal Coupling Facility (ICF)
򐂰An Integrated Facility for Linux (IFL)
򐂰A zSeries Application Assist Processor (zAAP)
The number of CPs and SAPs assigned for particular general purpose models depends on
the configuration. The number of spare PUs is dependent on how many CPs, SAPs, ICFs,
zAAPs, and IFLs are present in a configuration.
1.3.2 Memory
The minimum system memory on any model is 16 GB. Memory size can be increased in 8 GB
increments to a maximum of to 64 GB per book or 256 GB for the entire CPC. Each book has
two memory cards which come in three physical size cards: 8 GB, 16 GB, and 32 GB.
The z990 continues to employ storage size selection by Licensed Internal Code introduced on
the G5 processors. Memory cards installed may have more usable memory than required to
fulfill the machine order. LICCC will determine how much memory is used from each card.
1.3.3 Self-Timed Interconnect (STI)
An STI is an interface to the Memory Bus Adaptor (MBA), used to gather and send data. 12
STIs per z990 physical book is supported. Each of these STIs has a bidirectional bandwidth
of 2 GB/sec. The maximum instantaneous bandwidth per book is 24 GBytes/sec.
1.3.4 Channel Subsystem (CSS)
A new Channel Subsystem (CSS) structure was introduced with z990 to “break the barrier” of
256 channels. With the introduction of the new system structure and all of its scalability
benefits, it was essential that the Channel Subsystem also be scalable and allow “horizontal”
growth. This is facilitated by multiple Logical Channel Subsystems (LCSSs) on a single
zSeries server. The CSS has increased connectivity and is structured to provide the following:
– Four Logical Channel Subsystems (LCSS).
– Each LCSS may have from one to 256 channels.
– Each LCSS can be configured with 1 to 15 logical partitions.
– Each LCSS supports 63K I/O devices.
The I/O subsystem continues to be viewed as a single Input/Output Configuration Data Set
(IOCDS) across the entire system with multiple LCSS. Only one Hardware System Area
(HSA) is used for the multiple LCSSs.
A three-digit Physical Channel Identifier (PCHID) is being introduced to accommodate the
mapping of 1024 channels to four LCSS, with 256 CHPIDs each. CHPIDs continue to exist
and will be associated with PCHIDs. An updated CHPID Mapping Tool (CMT) is being
introduced and the CHPID report from e-config is replaced by a PCHID report. The CHPID
Mapping Tool is available from Resource Link™ as a standalone PC-based program.
Note: There is no change to the operating system maximums. One operating system
image continues to support a maximum of 256 channels, and has a maximum of 63K
subchannels available to it.