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. The supported upgrade paths for the z15 are shown in Figure 2-1. Table 2-1 z15 processor unit configurations Figure 2-1 z15 upgrade paths 20  IBM z15 Technical Introduction Feature  name Number of  CPC drawers Feature code Characterizable  processor units Standard  SAPs Spares Max34 1 0655 1 - 34 4 2 Max71 2 0656 1 - 71 8 2 Max108 3 0657 1 - 108 12 2 Max145 4 0658 1 - 145 16 2 Max190 5 0659 1 - 190 22 2