I recently upgraded to 4GB of RAM and I noticed that Windows Vista only reads 2.8GB while the BIOS reads the whole 4GB. After some testing, I then discovered that the higher 1GB or so is reserved for address mapping that's why a chunk of the whole memory isn't read by the OS. This is applicable to 32-bit operating systems; even if the theoretical maximum address lines tally to 4GB (2^32 = 4,294,967,296), there are still processes that diminish the total readable RAM. I was very irritated at first but then I realized that due to computer architecture limitations, it's something that we have to accept for now.
Read this article to know more:
http://blogs.msdn.com/hiltonl/archive/2007/04/13/the-3gb-not-4gb-ram-problem.aspxOne way to partially rectify this problemis using PAE and booting up using /3GB. But there are still hardware requirements before PAE could actually be used.
Comments or alternative solutions, anyone?