Different Windows editions have had different upper maximum RAM limits. 64-bit Windows support different amounts of memory as an SKU differentiating feature, with the low end being 512MB for Windows ...

I'm wondering what are the avantages of using a 64-bit CPU over a 32 bit one besides the huge amount memory it can address? From my understanding, most appications don't gain little it any performance ...

Now, the 64-bit thing, it's quite dramatic on the server because the cost of memory has come down so that putting huge amounts of physical memory on a server is economic and the demand for performance ...