This thread is a little confusing. You want to know how much RAM 64-bit supports, right? That has nothing to do with the mobo, even if it does limit the amount of RAM you can use, but 64-bit still supports more. If you want the exact number:

18,446,744,073,709,551,616 bytes.

It might look big, but I bet it will be considered an average amount of RAM to have in XX years.

jed-at-war

To clarify that magic number... The amount of ram an architecture supports is limited to it's memory adressing capability. A 32 bit instruction set has 32 bits with which to address memory blocks (which each hold a byte). Therefore a 32 bit machine can adress 2^32 different memory blocks which is 4,294,967,296 bytes. If you divide this number by 2^30 then you get your answer in gigabyes.

32-bit architecture supports 4 GB

With a 64 bit architecture you now have 64 bits for which to address memory. 2^64 is 18,446,744,073,709,551,616 bytes. If we divide that number by 2^30 we have our answer in GB. Divde by 2^40 and we have terabyes

64-bit architecture supports 17,179,869,184 GB which is 16,777,216 TB which is 16 exabytes.

This isn't to say this is what windows supports as they probably have all kinds of limits and other allocations going on.