What is the maximum RAM supported by the desktop and server editions?
Solution 1:
Maximum RAM supported by Ubuntu:
Ubuntu 32-bit + PAE (Physical Address Extension) - 64GB RAM although the memory access above 4GB will be slightly slower. PAE is now the standard for 32-bit Ubuntu, so there is no need for enabling it.
Ubuntu 64-bit - A 64-bit computer will be able to address up to 16.8 million TB (16 exabytes) although constraints are in place that limit this to around 1TB.
Reference: Ubuntu Documentation: 32-bit and 64-bit Community Help Wiki