The z17 version of the IBM z/Architecture Principles of Operation (SA22-7832-14), the IBM z/Architecture Reference Summary (SA22-7871-12), and other z17-related architecture documentation can be found at the following (thanks for the link Bruce):
https://www.ibm.com/docs/en/systems-hardware/zsystems/9175-ME1?topic=library-2 I've successfully downloaded both without any sort of logon or IBM ID required.
