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/  **
*************************************************************************

Reply via email to