64-bit binary operations

64-bit binary operations perform arithmetic and logical operations on 64-bit binary values. 64-bit AMODE allows access to storage operands that reside anywhere in the 16-exabyte address space. In support of both, z/Architecture® extends the GPRs to 64 bits. There is a single set of 16 64-bit GPRs, and the bits in each are numbered from 0 to 63.

All S/390® instructions are carried forward into z/Architecture and continue to operate using the low-order half of the z/Architecture 64-bit GPRs. That is, an S/390 instruction that operates on bit positions 0 through 31 of a 32-bit GPR in S/390 operates instead on bit positions 32 through 63 of a 64-bit GPR in z/Architecture. You can think of the S/390 32-bit GPRs as being imbedded in the new 64-bit GPRs.

Throughout the discussion of GPRs, bits 0 through 31 of the 64-bit GPR are called the high-order half, and bits 32 through 63 are called the low-order half.

The purpose of this information is help you use the 64-bit GPR and the 64-bit instructions as you want to save registers, perform arithmetic operations, access data. It is not a tutorial about how to use the new instruction set. Principles of Operation is the definitive reference information for these instructions. This information, however, describes some concepts that provide the foundation you need. After you understand these, you can go to Principles of Operation and read the introduction to z/Architecture and then refer to the specific instructions you need to write your program.