“Some of the most important changes in Linux 2.4 relate to
hardware and software architecture. With 2.4, the kernel now
supports as much as 64 GB of memory on Intel x86-compatible systems
that support physical address extension (PAE), which includes
systems based on the Pentium Pro and subsequent processors. While
few desktop users will find themselves needing to use 64 GB of RAM,
enterprise-class systems that must support thousands of
simultaneous users demand more memory than the comparatively paltry
2 GB supported by Linux 2.2.”
“The ability to use lots of RAM should also be a major boon to
those who wish to use Linux with large databases. Database query
and access times drop significantly when more of the database can
be located in RAM rather than being fetched from disk.”
“Linux 2.4 also increases and improves Linux support for
symmetric multiprocessing (SMP). Linus reports that it is “painful”
for him to go back to using the 2.2 kernel on multiprocessor
machines. 2.4 should be optimized for machines with up to eight
processors, but some parties (notably Linuxcare) are reported to
have 2.4 working on machines with up to 64 processors.”