One might expect a multitasking OS like Linux, which frequently grabs instructions and data from all over in memory, to attenuate the benefits of cache, but the granulation of multitasking systems is large enough that the effect is minimal, especially on fast processors. That is, dynamic RAM loses its charge and constantly requires refreshing, and if the RAM refresh is synced to the speed of the processor's system bus, a noticeable performance improvement can be made. Although it doesn't translate into a monstrous performance increase, especially because of the very high speeds of L1 and L2 cache and the efficiency of this system, at the very least it's not a weak link. Intel Pentium III Xeon 550MHz chips, though one is by no means compelled to choose such a setup. At the moment, VA Linux offers a range of processors starting with Intel's Celeron 400MHz and ranging up to 600MHz Pentium IIIs and 550MHz Xeons.
Workstations have one or two processors, servers are available with four, and clusters have more.
The Linux kernel can take advantage of two processors and is said to do well with four, although it is rumored more might be gratuitous and a bit less efficient than distributed computing. The difference between various chips can be confusing. Xeon is the futuristic name given to the top of the Pentium line, designed for server applications. Xeons are made for multiprocessing and use 100MHz buses and 32KB of L1 cache via a 64-bit bus, with support for larger addresses for dealing with big machines. Xeon 36-bit addressing, for example, can access 64GB of physical memory, which may be 62GB more than Linux kernels support.