IBM 990 - Manual (Page 15)

Chapter 1. zSeries 990 overview 3
1.1 Introduction
The z990 further extends and integrates key platform characteristics: dynamic and flexible
partitioning, resource management in mixed and unpredictable workload environments,
availability, scalability, clustering, and systems management with emerging e-business on
demand application technologies (for example, WebSphere®, Java™, and Linux).
The zSeries 990 family provides a significant increase in performance over the previous
zSeries servers. The z990 introduces a different design from its predecessor, the zSeries
900. One noteworthy change is to the CEC cage, which is capable of housing up to four
books. This multi-book design provides enough Processor Units to improve total system
capacity by nearly three times over that provided by z900.
Figure 1-2 Introducing the z990 - internal and external view
The z990 introduced the superscalar microprocessor architecture. This design, and the
exploitation of the CMOS 9SG-SOI technology, improves the uniprocessor performance by
54% to 61%, compared to z900 Model 2C1. However, the true capacity increase of the
system is driven by the increased number of Processor Units per system: from 20 in the z900
to 48 Processor Units in the z990. The 48 Processor Units are packaged in four MCMs with
12 Processor Units each, plus up to 64 GB of memory and 12 STI links per book. All books
are connected via a super-fast redundant ring structure and can be individually upgraded.
The I/O infrastructure has been redesigned to handle the large increase in system
performance. The multiple Logical Channel Subsystems (LCSS) architecture on the z990
allows up to four LCSS, each with 256 channels. Channel types supported on the z990 are:
FICON Express
Coupling Links
OSA-Express
ESCON®