"The L in AIX 5L stands for Linux affinity, which means
that many of the Linux APIs are supported within AIX so
applications written for Linux can be recompiled to run natively on
PowerPC and Power4 processors. IBM had originally intended to offer
the ability to run Linux binaries compiled for Intel processors on
AIX 5L, but this part of the operating system never got off the
ground because of the performance penalties involved with running
emulated X86 instructions on the IBM Power chip architecture.
AIX 5l V5.1 includes support for Power4 processors, 32-way
symmetric multiprocessing, rudimentary static logical partitions,
256Gb of main memory, and 64-bit AIX kernel and drivers. The prior
AIX 4.3 releases supported 24-way SMP and 96Gb of main memory and
had support for some 64-bit APIs.
According to sources familiar with IBM's plans, AIX 5L V5.2 will
have support for dynamic logical partitions - presumably only on
Power4-based pSeries 690 servers, but perhaps also on S-Star
PowerPC-based pSeries 680 servers."