IBM eServer zSeries 990 Technical Guide

24 IBM ^ zSeries 990 Technical Guide

2.1 System structure

The z990 structure and design are the result of the continuous evolution of S/390 and zSeries

since CMOS servers were introduced in 1994. The structure and design have been

continuously improved, adding more capacity, performance, functionality, and connectivity.

The objective of z990 system structure and design is to offer a flexible infrastructure to

accommodate a wide range of operating systems and applications, whether they be

traditional or emerging e-business applications based on WebSphere, Java, and Linux, for

integration and deployment in heterogeneous business solutions.

For that purpose, the z990 introduces a superscalar microprocessor architecture, improving

uniprocessor performance, and providing an increase in the number of usable processors per

system. In order to keep a balanced system, the I/O bandwidth and available memory sizes

have been increased accordingly.

2.1.1 Book concept

The z990 Central Processor Complex (CPC) introduces a packaging concept based on

books. A book contains processors (PUs), memory, and connectors to I/O cages and ICB-4

links. Books are located in the CEC cage in Frame A. A z990 server (CPC) has at least one

book, but may have up to four books installed.

A book and its components is shown in Figure 2-1. Each book contains:

򐂰 12 Processor Units (PUs). The PUs reside on microprocessor chips located on a

Multi-Chip Module (MCM).

򐂰 16 GB to 64 GB physical memory. There are always two memory cards, each containing

8, 16, or 32 GB.

򐂰 Three Memory Bus Adapters (MBAs), supporting up to 12 Self-Timed Interconnects

(STIs) to the I/O cages and/or ICB-4 channels.

Figure 2-1 Book structure and components

Up to four books can reside in the CEC cage. Books plug into cards, which plug into slots of

the CEC cage board.

STI Slots

MCM

Memory cards

Chapter 2. System structure and design 25

Power

Each book get its power from two Distributed Converter Assemblies (DCA) that reside on the

opposite side of the CEC board. The DCAs provide the required power for the book. Each

book is supported by two DCAs. The N+1 power supply design means that there is more DCA

capacity than is required for the book. If one DCA fails, the power requirement for a book can

still be satisfied from the remaining DCA. The DCAs can be concurrently maintained, which

means that replacement of one DCA can be done without taking the book down.

Between two sets of DCAs you find the location of the oscillator cards (OSC) and the optional

external time reference cards (ETR). If installed, there are two ETR ports to which an optional

Sysplex Timer® can be connected. Seen from the top, the packaging of a four-book system

appears as shown (schematically) in Figure 2-2.

Figure 2-2 Book and power packaging (top view)

Located within each book is a card on which the Memory Bus Adapters (MBAs) are located.

The card has three MBAs, each driving four STIs (see Figure 2-8 on page 32).

Figure 2-2 also illustrates the order of book installation:

򐂰 In a one-book model, only book 0 is present.

򐂰 A two-book model has books 0 and 1.

򐂰 A three-book model has books 0, 1, and 2.

򐂰 A four-book model has books 0, 1, 2, and 3.

Book installation to up to four books can be concurrent.

Cooling

The z990 is an air-cooled system assisted by refrigeration. Refrigeration is provided by a

closed-loop liquid cooling subsystem. The entire cooling subsystem has a modular

construction. Its components and functions are found throughout the cages, and are made up

of three subsystems:

1. The Modular Refrigeration Units (MRU)

– One or two MRUs (MRU0 and MRU1), located in the front of the A-cage above the

books, provide refrigeration to the content of the books together with Motor Drive

Assemblies in (MDAs) in the rear.

– A one-book system has MRU0 installed. Upgrading to a two-book system causes

MRU1 to be installed, providing all refrigeration needs for a four-book system.

Concurrent repair of an MRU is possible by taking advantage of the hybrid cooling

implementation described in the next section.

DCA00

DCA01

DCA11

DCA10

DCA21

DCA20

DCA31

DCA30

DCA01

2xOSC 00/01 2xETR 00/01

Book3

Book0

Book1

Book2

Memory Cards

Memory Cards

Memory Cards

Memory Cards

MCM

MCM

MCM

MCM