The first group represents the processor type -- 2817 is zEnterprise 196.
The second group represents the model and varies widely by processor type. It identifies the processing power (number and type of CPUs) of the box.
The serial number is a serial number.
Example for the z10:
Enterprise Class
Released on February 26, 2008, the System z10 Enterprise Class is available in five hardware models: E12, E26, E40, E56, and E64. Each is of the machine type 2097.[2] The Enterprise Class PU cores (four per chip) operate at speeds of 4.4 GHz. The processors are stored in one to four compartments referred to as "books". Each book comprises a multi-chip module (MCM) of processing units (PUs) and memory cards (including multi-level cache memory). The number of PUs in each book is based upon the model number:[3]
Model Books / PUs CPs IFLs / uIFLs zAAPs / zIIPs ICFs Opt SAPs Std SAPs Std Spares Standard Memory (GB) Flexible Memory (GB)
E12 1 / 17 0-12 0-12 / 0-11 0-6 / 0-6 0-12 0-3 3 2 16 - 352 NA
E26 2 / 34 0-26 0-26 / 0-25 0-13 / 0-13 0-16 0-7 6 2 16 - 752 32 - 352
E40 3 / 51 0-40 0-40 / 0-39 0-20 / 0-20 0-16 0-11 9 2 16 - 1136 32 - 752
E56 4 / 68 0-56 0-56 / 0-55 0-28 / 0-28 0-16 0-18 10 2 16 - 1520 32 - 1132
E64 4 / 77 0-64 0-64 / 0-63 0-32 / 0-32 0-16 0-21 11 2 16 - 1520 32 - 1136