Mark is correct. 4 GB is a physical limitation of 32-bit kernels, which is the best reason to go 64-bit: no real limitation to the amount of RAM you can use, other than what the motherboard will support. However, I can recall when 32-bit came around in the 90's, "Wow! 4 GB of RAM! We'll never see that in our lifetime."
Amiga was 32-bit very early, correct? PAE is a workaround for datacenter systems. From Tony's wiki link: "x86 processor hardware architecture is augmented with additional address lines used to select the additional memory, so physical address size is increased from 32 bits to 36 bits. This, theoretically, increases maximum physical memory size from 4 GB to 64 GB. The 32-bit size of the virtual address is not changed, so regular application software continues to use instructions with 32-bit addresses and (in a flat memory model) is limited to 4 gigabytes of virtual address space. The operating system uses page tables to map this 4 GB address space into the 64 GB of virtual memory. The mapping is typically applied differently for each process. In this way, the extra memory is useful even though no single regular application can access it all simultaneously. For example, in Windows, x86, 32-bit-versions, the maximum 4GB of virtual address space (VAS) is separated into two sections of 2GB: 2GB is allocated to kernel processing and the other 2GB is allocated to user. Regardless of how much physical RAM a Windows, x86, 32-bit-version computing system has, the VAS is still limited to 4GB. However, this is not true for Windows, x64-versions - which incidentally have up to 16TB of VAS." > -----Original Message----- > Do you understand binary numbers, Tony? A 32-bit binary number cannot > go beyond 4,294,967,296 (4 gigabytes, 4*1024*1024*1024), so a 32-bit > system cannot address more than 4 GB. ************************************************************************* ** List info, subscription management, list rules, archives, privacy ** ** policy, calmness, a member map, and more at http://www.cguys.org/ ** *************************************************************************