I meant RAM cacheable by machine. Until the Pentium II, which had an integrated cache controller, it was common for motherboard manufacturers to cache less than the full potential amount to save a little money on components (specifically, something called Tag RAM). Looking up your board, it does appear to exhibit this problem, though at 128 MB rather than the more common 64 MB:
http://www.anandtech.com/show/116
This would mean that you could increase performance by removing memory. A common workaround back in the day was to create a RAM drive in the uncached region and use it as swap.