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## 2.1 Models and upgrade paths 

The IBM z15 (machine type 8561) has one model: the T01. The maximum number of characterizable processors is represented by feature names Max34, Max71, Max108, Max145, and Max190. 

As with its predecessors, the z15 Central Processor Complex (CPC) is built by using a processor unit (PU) with single chip modules (SCMs). Each SCM can have 9 - 12 active processor unit cores. Spare PUs, system assist processors (SAPs), and one integrated firmware processor (IFP) are included in the z15 configuration. 

The number of characterizable PUs, SAPs, and spare PUs for the various features is listed in Table 2-1. For more information about PU characterization types, see “PU characterization” on page 27. 

<img src='content_image/982968.jpg'>

The supported upgrade paths for the z15 are shown in Figure 2-1. 

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