Perhaps the major changes introduced by this new kernel happened in the architecture. In general, the 2.4 kernel lifts Linux into what has been traditionally termed as the enterprise market. In other words, the new kernel adds scalability to the operating system.
How so? Well, the 2.4 kernel scales up to 64 GB of memory if necessary, which is undoudtedly a big step forward compared to the 2 GB limit of the previous 2.2 kernel. Of course, one of the main applications of this major improvement will be the use of Linux for huge databases.
Additionally, Linux 2.4 improves the support for symmetric multi-processing (SMP). The previous kernel already included this support, but many complained that it was not truly stable and scalable. The new kernel can work on machines that have up to 64 processors, thus perhaps making it possible for Linux to compete with other operating systems that have traditionally owned the big iron market. IBM and SGI are positioned to gain quite a bit from this move if Linux proves to be reliable enough in this field, since they have been betting on it for a while now.
Other significant improvements are: