All page and chapter references in this document refer to:
IBM Redbook - IBM System z9 Enterprise Class Technical Guide - SG24-7124
Book Concept
The z9 EC
Central Processor Complex (CPC) uses packaging concept based on books.
A book contains:
-
processors (PUs)
-
memory
-
connectors to I/O cages and ICB-4 links
Books provide:
-
Power
-
Timer functions
-
Cooling
Books are located in the CEC cage in Frame A. A z9 EC server has at least one book, but may have up to four books installed. A book and its components are shown in Figure 2-1. Each book contains:
Up to four books can reside in the CEC cage. Books plug into cards, which plug into slots of the CEC cage board.
Power
Each book get its power from two Distributed Converter Assemblies (DCA) that reside on the opposite side of the processor 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.
Timer Oscillators
Two oscillator cards (OSC) and the two optional external time reference cards (ETR) are located between two sets of DCAs. If installed, there are two ETR ports to which an optional Sysplex Timer can be connected.
The two oscillator cards act as a primary and a backup. In case the primary oscillator card would fail, the backup card detects the failure and continues to provide the clock signal so that no outage due to an oscillator failure is taken.
Seen from the top, the packaging of a four-book system appears as shown (schematically) in Figure 2-2.
Located within each book are nine cards, eight of which are Memory Bus Adapter/STI fanout cards. Each fanout card drives two STIs, for a total of 16 STI connections to the I/O cages and/or ICB-4 channels (see Figure 2-6 on page 35).
The Figure 2-2 order of book installation is:
Book installation from one to up to four books is concurrent.
Cooling
The z9 EC 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:
-
– 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.
The Motor Drive Assembly (MDA)
MDAs are found throughout the frames to provide air cooling where required. They are located at the bottom front of each cage, and in between the CEC cage and I/O cage, one in combination with the MSAs.
Hybrid cooling system
The z9 EC has a hybrid cooling system that is designed to lower power consumption. Normal cooling is provided by one or two MRUs connected to the heat sinks of all MCMs in all books. If one of the MRUs fails, backup MSAs are switched in to compensate for the lost refrigeration capability with additional air cooling. At the same time, the oscillator card is set to a slower cycle time, slowing the system down by up to 10 percent of its maximum capacity, to allow the degraded cooling capacity to maintain the proper temperature range. Running at a slower cycle time, the MCMs produce less heat. The slowdown process is done in steps, based on the temperature in the books.
Figure 2-3 shows the refrigeration scope of MRU0 and MRU1.
