This site summarises it well and links to an M$ knowledge base article:
http://www.memorystock.com/windows-memory.html
You really should upgrade to XP. Win98 can't use the RAM.
Hoo, hoo there. Win98 should be fine with 1GB ram. If it isn't, you've
****ed it too much with 'tuning' utilities.
But above 512MB (or even sooner if, you've got a large AGP aperture)
you should limit the diskcache!
(there's no benefits to a larger agp aperture than 64MB)
in the System.ini file:
MinFileCache=262144
MaxFileCache=524288
if you've got more than 512MB ram.
The article seem to seriously misunderstand some things, about
memoryhandling, mapping and the Vcache! You do NOT get slower memory
access for larger ram!
Ancra