A method of configuring IA-32 computer resources accommodates multiple
operating systems and memory sizes automatically. If total available
physical memory does not exceed 4 GB, then the minimum required
memory-mapped IO size is rounded up to the next multiple of 128 M.
Otherwise, it is rounded up to the next multiple of x, where x is a
function of the number of DIMM socket pairs available. TOLM is set to 4
GB minus the rounded memory-mapped IO size. For operating systems that
can address only up to 4 GB, the method chooses an acceptable value for
TOLM because the granularity used to choose it is reasonably small--128
MB. For operating systems that can address more than 4 GB, the method
chooses an exceptionally good value for TOLM: Regardless of the amount of
memory available, the BIOS can define caching characteristics for all of
the memory using at most 6 MTRR pairs.