IBM 990 Manuel D’Utilisation

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Chapter 1. IBM zSeries 990 overview 
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Draft Document for Review April 7, 2004 6:15 pm
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change the PU characterization of the server they are upgrading. In addition, customers who 
are consolidating may not be increasing total capacity, and/or they may wish to take 
advantage of the multiple Logical Channel Subsystems offered. z990-to-z990 model 
upgrades and feature adds may be completed concurrently. 
Model downgrades 
There are no model downgrades offered. Customers may purchase unassigned CPs or IFLs 
for future use. This avoids the placement of RPQ orders and subsequent sequential MES 
activity, and paying software charges for capacity that is not in use.
Concurrent Processor Unit (PU) conversions
z990 servers support concurrent conversion between different PU types, providing flexibility 
to meet changing business environments. Assigned CPs, unassigned CPs, assigned IFLs, 
unassigned IFLs, and ICFs may be converted to assigned CPs, assigned IFLs or ICFs, or to 
unassigned CPs or unassigned IFLs.
1.3  System functions and features
The 990 system offers the following functions and features.
1.3.1  Processor
IBM introduced the Processor Resource/Systems Manager™ (PR/SM) feature in February 
1988, supporting a maximum of four logical partitions. In June 1992, IBM introduced support 
for a maximum of 10 logical partitions and announced the Multiple Image Facility (MIF, also 
known as EMIF), which allowed sharing of ESCON channels across logical partitions—and 
since that time has allowed sharing of more channels across logical partitions (such as 
Coupling Links, FICON and OSA). In June 1997, IBM announced increased support - up to 
15 logical partitions on Generation 3 and Generation 4 servers. 
The evolution continues and IBM is announcing support for 30 logical partitions. This support 
is exclusive to z990 and z890 models.
MCM technology
The z990 12-PU MCM is smaller and more capable than the z900’s 20-PU MCM. It has 
16 chips, compared to 35 for the z900. The total number of transistors is over 3 billion, 
compared with approximately 2.5 billion for the z900. With this amazing technology 
integration comes improvements in chip-to-substrate and substrate-to-board connections. 
The z990 module uses a connection technology, LAN Grid Arrays (LGA), pioneered by the 
pSeries™ in the p690 and the i890. LGA technology enables the z990 substrate, with only 
53% of the surface area of the z900 20 PU MCM substrate, to have 23% more I/Os from the 
logic package. 
Both the z900 and z990 have 101 layers in the glass ceramic substrate. The z990's substrate 
is thinner, shortening the paths that signals must travel to reach their destination (another chip 
or exiting the MCM). Inside the low dielectric glass ceramic substrate is 0.4 km of internal 
wiring that interconnects the 16 chips that are mounted on the top layer of the MCM. The 
internal wiring provides power and signal paths into and out of the MCM. 
The MCM on the z990 offers flexibility in enabling spare PUs via the Licensed Internal Code 
Configuration Control (LIC-CC) to be used for a number of different functions. These are:
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A Central Processor (CP)