The IBM z14 processor is generally available today (14 September 2017). The z/Architecture Principles of Operation corresponding to the new z14 processor is available at http://publibfp.dhe.ibm.com/epubs/pdf/dz9zr011.pdf
The z/Architecture Reference Summary corresponding to the new z14 processor is available at http://publibfp.dhe.ibm.com/epubs/pdf/dz9zs009.pdf
