The 64-bit Large Data Type (LDT) Application Binary Interface (ABI), or 64-bit LDT ABI, increases scalability for 64-bit applications, while maintaining binary compatibility for existing 32-bit applications. To accomplish this, some system- derived types are increased from 32-bits to 64-bits. In addition, a new 64-bit magic number is being introduced in the XCOFF definition to identify object code files using the new 64-bit ABI.
The AIX 4.3 64-bit, non-LDT, ABI is no longer supported on AIX 5.1. Object code files with the old 64-bit magic number will not link, load, or execute. Pre-AIX 5.1 64-bit applications must be recomplied in order to execute them on AIX 5.1. Binary compatibility will be preserved for 32-bit objects generated on all earlier levels of AIX, regardless of LDT support. Mod-level 1.3.4 of the SMP Run-Time Library (xlsmp.rte) must be available in order to use SMP functionality on AIX 5.1.