I am confuse about memory configuration, i have below questions. 1.if 32-bit os maximum virtual address is 4GB, When i have 4 gb of ram for 32-bit os, What about the virtual memory size ? is it required virtual memory(disk space) or we can directly use physical memory ? 2.In 32-bit os 12 bits are offset because page size=4k i.e 2^12 and 2^20 for page addresses What about 64-bit os, What is offset size ? What is page size ? How it calculated. 3.What is PAE? If enabled how to decide size of PAE, what is maximum and minimum size of extended memory. Regards, Pankaj